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The Effect of a patellofemoral knee brace on quadriceps muscle activity

University of Florida Institutional Repository

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THE EFFECT OF A PATELLOFEMORAL KNEE BRACE ON QUADRICEPS MUSCLE ACTIVITY By MADELON CAROL HASKIN A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN EXERCISE AND SPORTS SCIENCE UNIVERSITY OF FLORIDA 2003

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Copyright 2003 by Madelon Carol Haskin

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ACKNOWLEDGMENTS I would like to take this opportunity to thank the numerous people who are responsible for making this project possible. Without the cooperation, guidance, and support of everyone around me, its completion would not have been possible. I would first like to thank Dr. Powers for his help as committee chair. He was an endless source of information and new ideas that aided me in my successful completion of this thesis. I would also like to thank the members of my supervising committee. Dr. Horodyski provided support and guidance in getting this project off the ground and I thank her for this. She was also a valuable source of information, and her knowledge of this topic contributed to its conclusion. Dr. Siders was also an important source of information to improve my project. His knowledge of statistics was a helpful addition to the data analysis of this topic. I would like to thank both Dr. Horodyski and Dr. Siders for their patience towards the end of the project. My gratitude goes out to Matthew Morgan for his role as my doctoral mentor. These past two years have taken their toll, and Matts availability has made it possible to complete my master's work. As a novice at research, I depended on him, time and again, to guide me. The long hours of data collection for this project could not have been completed without the help of my colleagues and friends. I would like to thank Kyle Smink for his patience in sharing the lab equipment, as well as Dennis Valdez for his assistance during iii

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data collection. My gratitude also goes to the SW Rec Center for the availability of the facilities during testing. Without the voluntary participation of all the subjects, the project would not have been possible. Therefore, I would like to thank all of the men and women who completed the exercise protocols for this project. I would also like to thank my cousins Amy, Kim, and Joi for being such good listeners and problem solvers. Without their help I would not have made it through this thesis. My uncle Joe and Aunt Dawn have also been a much needed support. Finally, I thank my parents, Edward and Julia, and my brother, Eric, for the twenty-four years of unconditional love and support. Without them, I would never have made it to this point. Regardless of the obstacles I face, they give me the strength to pull through with their ceaseless love and encouragement. iv

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TABLE OF CONTENTS page ACKNOWLEDGMENTS.................................................................................................iii LIST OF TABLES............................................................................................................vii LIST OF FIGURES.........................................................................................................viii ABSTRACT.......................................................................................................................ix CHAPTER 1 INTRODUCTION........................................................................................................1 Statement of the Problem..............................................................................................2 Hypotheses....................................................................................................................3 Definition of Terms......................................................................................................3 Assumptions.................................................................................................................4 Limitations....................................................................................................................4 Significance of Study....................................................................................................5 2 REVIEW OF LITERATURE.......................................................................................6 Patellofemoral Pain Syndrome.....................................................................................6 Anatomy.......................................................................................................................7 Contributing Factors of PFPS.......................................................................................8 Malalignment.........................................................................................................9 Muscular Imbalance..............................................................................................9 Patellar Tracking.................................................................................................10 Vastus Medialis Oblique.....................................................................................10 Treatment for Patellofemoral Pain..............................................................................11 Operative.............................................................................................................11 Non-operative......................................................................................................12 Quadriceps strengthening.............................................................................13 Patellofemoral taping...................................................................................15 Patellofemoral bracing.................................................................................17 Electromyography.......................................................................................................21 3 METHODS.................................................................................................................24 Subjects.......................................................................................................................24 v

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Instrumentation...........................................................................................................24 Electromyography (EMG)...................................................................................24 Patellofemoral Knee Brace..................................................................................25 Measurements.............................................................................................................25 One Repetition Maximum (1-RM)......................................................................25 Muscle Activity...................................................................................................25 Procedures...................................................................................................................26 Data Analysis..............................................................................................................27 4 RESULTS...................................................................................................................28 Subject Demographics................................................................................................28 Vastus Medialis..........................................................................................................28 Vastus Lateralis..........................................................................................................30 5 DISCUSSION.............................................................................................................32 Vastus Medialis..........................................................................................................32 Vastus Lateralis..........................................................................................................33 Patellofemoral Bracing...............................................................................................33 Patellofemoral Taping................................................................................................36 Exercise Comparison..................................................................................................37 Clinical Implications...................................................................................................40 Summary.....................................................................................................................41 Implications for Future Research................................................................................42 APPENDIX A UNIVERSITY OF FLORIDA INSTITUTIONAL REVIEW BOARD.....................43 B INFORMED CONSENT............................................................................................46 C DATA SHEET............................................................................................................48 D ANOVA TABLES......................................................................................................49 LIST OF REFERENCES...................................................................................................50 BIOGRAPHICAL SKETCH.............................................................................................56 vi

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LIST OF TABLES Table page 4.1 Subject demographics (means SD)........................................................................28 4.2 Normalized VM activity during OKC and CKC knee extension (Mean SD)........29 4.3 Normalized VM activity during braced and unbraced conditions (Mean SD)......29 4.4 Normalized VL activity during OKC and CKC knee extension (Mean SD).........30 E-1 ANOVA test results for VM....................................................................................49 E-2 ANOVA test results for VL.....................................................................................49 vii

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LIST OF FIGURES Figure page 5-1 VM EMG activity during braced conditionsignificantly greater than the Unbraced Condition (P 0.05)................................................................................34 5-2 Concentric 45 to 0 of knee flexion during CKC and OKC exercises significant interaction (P 0.05)................................................................................................38 5-3 Eccentric 45 to 90 of knee flexion during CKC and OKC exercises significant interaction (P 0.05)................................................................................................39 viii

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Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science THE EFFECTS OF A PATELLOFEMORAL KNEE BRACE ON QUADRICEPS MUSCLE ACTIVITY By Madelon Carol Haskin August 2003 Chair: MaryBeth Horodyski Major Department: Exercise and Sport Sciences Patellofemoral pain syndrome (PFPS) is one of the most common musculoskeletal disorders seen in sports medicine clinics today. The basic etiology of this syndrome remains unknown. The exact cause of PFPS has been thought to vary from patient to patient; therefore, a thorough investigation of history for each patient is necessary. The methods to treat PFPS vary greatly ranging from quadricep strengthening to patellofemoral bracing. Research has been conducted on the effects of the patellofemoral brace on patellar alignment, but little is known on the effect of the patellofemoral brace on quadriceps muscle activity. Therefore, the purpose of the present study was to assess the effect of a patellofemoral knee brace on quadriceps muscle activity. Twenty-three health subjects who had no history of previous knee injury participated in this study. Prior to testing, each subjects 1-maximum repetition (1-RM) for CKC(leg press), and OKC exercises (knee extension), were recorded. At least 48 hours later the subjects returned for testing. Electromyographic (EMG) electrodes were ix

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placed over the non-dominant legs vastus medialis (VM) and vastus lateralis (VL) muscles, as well as the patella. A three-minute warm-up on a stationary bike was followed by 5 repetitions of both the knee extension and leg press exercises performed at 75% of the subjects 1-RM. The order of conditions was randomized prior to testing. Muscle activity was recorded using surface EMG during the concentric and eccentric phases of each exercise. The data were analyzed to identify interactions. The analyses demonstrated no significant interactions between knee extension and leg press exercises during the braced and unbraced conditions. However, there was a significant main effect between the braced and unbraced conditions regardless of exercise type and phase of exercise. The results revealed greater muscle activation during the braced condition versus the unbraced condition suggesting that a patellofemoral brace positively effects muscle activity. Further research is needed to assess the effects a patellofemoral knee brace on quadricep muscle activity during OKC and CKC exercises with patellofemoral pain subjects. x

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CHAPTER 1 INTRODUCTION The knee is a very important joint in the body, being involved in locomotion and stability of the lower extremity.10 The knees involvement in locomotion causes it to be a common site for injury. These injuries can be painful and often debilitating taking an athlete out of competition. Patellofemoral pain syndrome (PFPS) is one of the most common musculoskeletal disorders affecting young adults.3,4 PFPS is often misdiagnosed as anterior knee pain, chondromalacia patella, patellar pain syndrome, patellofemoral arthralgia, patellar pain, and patellarfemoral pain.55 The basic etiology of this syndrome is still unknown, but numerous predisposing factors have been mentioned in the literature.42,55 Many muscles work together to enable the knee joint to be functional. The main muscle groups are the pes anserinus, hamstrings, and the quadriceps. The pes anserinus muscle group consists of the gracillis, sartorius, and the semitendinosus (a hamstring muscle). The hamstrings are composed of the semitendinosus, semimembranosus, and biceps femoris. The quadriceps include the vastus medialis, vastus lateralis, vastus intermedius, and rectus femoris. The vastus medialis obliquus muscle (VMO) of the quadriceps muscle group has been thought to be a major contributor to patellofemoral joint pain. The VMO pulls the patella medially during knee extension and has been reported to fire later than the vastus lateralis (VL) in people with patellofemoral joint pain.55 This firing pattern may effect patellar tracking, causing the patella to track laterally because the VMO is not firing on 1

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2 time. Exercises that focus on VMO activity are emphasized to normalize the VMO:VL firing ratio to correct the patellar tracking pattern. Reducing the abnormality of this ratio has been thought to decrease patellofemoral joint pain.55 Knee braces, specifically patellar braces, have been thought to help with this process. The patellofemoral knee brace places pressure on the lateral side of the patella to deter lateral movement.4,42,55 There has been much debate on what type of rehabilitation program should be implemented for athletes with patellofemoral pain. Treatment techniques frequently used include quadriceps exercises focusing on the VMO, patellar taping, electrical stimulation to guide quadriceps exercises, nonsteroidal anti-inflammatory agents, and patellofemoral knee braces.3,28,49,59 A consensus on which rehabilitation program works best has not been reached. Knee pain is a common complaint in sports medicine clinics, accounting for 23 to 31% of the injuries. Of that percentage patellofemoral joint pain is the most common.55 The high volume of patellofemoral injuries makes it important to understand the many different ways to treat them. Previous studies have addressed the efficacy of patellofemoral knee braces for the prevention or treatment of anterior knee pain.3,4,42 Only one study had been found that investigated muscle activity, and muscle activity changes, while wearing a knee brace.23 Therefore, it becomes important to expand upon previous research to understand what is happening muscularly while wearing a knee brace. Statement of the Problem The VMO is a major focus in the rehabilitation of patellofemoral pain; strengthening the VMO and improving the firing sequence with the VL are primary concerns.1,3,7 While an athlete is progressing through rehabilitation, it is common practice

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3 to have them wear a knee brace to facilitate greater medial tracking. The knee brace has been shown to improve medial tracking, but the ramifications of potential changes in VMO activity while wearing the brace have not been thoroughly studied.42 It has been theorized that the VMO may not be as active while wearing the knee brace.23 Since the brace is pushing the patella medially during knee extension, the VMO does not have to work to pull the patella medially. If this is true, the knee brace may interfere with VMO training during functional rehabilitation. Therefore, the purpose of this study was to collect data on VMO and VL activity using surface electromyography (EMG) during exercises, with and without a patellofemoral knee brace. Hypotheses Five hypotheses were identified for this investigation. Vastus medialis (VM) and Vastus lateralis (VL) muscle activity will be reduced while wearing a knee brace as compared to not wearing a knee brace. Open kinetic chain (OKC) exercises will have greater VM and VL muscle activity as compared to closed kinetic chain (CKC) exercises when performed without a knee brace. OKC exercises will have greater VM and VL muscle activity as compared to CKC exercises when performed with a knee brace OKC exercises will have greater VM and VL muscle activity as compared to CKC exercises during the first 45 of motion when performed without a knee brace. OKC exercises will have greater VM and VL muscle activity as compared to CKC exercises during the first 45 of motion done with a knee brace. Definition of Terms Four definitions were identified for this investigation. Closed kinetic chain (CKC) a movement whereby the foot or hand is on the ground or some other surface.2 For the purpose of this study, the CKC exercise involves the use of the leg press machine.

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4 Malalignment lower extremity alignment factors associated with PFPS include femoral neck anteversion, genu valgum, knee hyperextension, Q angle, tibia varum, and excessive rearfoot pronation.55 Open kinetic chain (OKC) a movement whereby the foot or hand is off the ground.2 For the purpose of this study, OKC involves the use of the lower extremity performing concentric and eccentric knee extensions on the knee extension machine. Patellofemoral Pain Syndrome (PFPS) anterior knee pain that is often diffuse and along the medial aspect of the patella. Later, patellar pain and retropatellar pain are also seen.44 Assumptions Five assumptions were identified for this investigation. It was assumed that the subjects accurately performed all testing procedures as instructed by the tester. It was assumed that the subjects performed all the testing procedures/exercises to the best of their ability. It was assumed that all subjects gave accurate and honest answers to the medical history questionnaire. It was assumed that the surface EMG detected and displayed accurate quadriceps activity during the exercises. It was assumed that the brace remained in the proper location on the subject throughout testing. Limitations Three limitations were identified for this investigation. All of the subjects tested had healthy knees with no previous history of patellofemoral pain. Therefore, the subjects did not normally wear a patellofemoral knee brace. Subjects may not have performed to their best ability during testing procedures. The subjects being tested did not have prior experience with a knee brace; therefore, they were not acclimatized to the feel of exercise while wearing a knee brace. Accommodation of the knee brace was not possible due to the limitation of available knee braces.

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5 Significance of Study All rehabilitation programs should incorporate a functional aspect where the rehabilitation exercises specifically mimic their sport. It is important to ensure that the necessary muscles are being targeted during these functional exercises thereby enhancing the rehabilitation process. Athletes with patellofemoral pain often continue to participate in their chosen sport while going through a rehabilitation program. In order for continued participation, the athletes may wear a knee brace to help decrease the pain during the activity. Only one study had been found that determined the changes of muscular activity while wearing a knee brace during open chain activities,19 while no known studies we found that investigated CKC exercises. Does the knee brace prolong the rehabilitation process by not allowing the VMO to be functionally rehabilitated? It is important for athletic trainers to know if the application of a knee brace decreases the firing of the VMO. The results of this study may give athletic trainers and rehabilitation specialist the answer they need to adjust patellofemoral rehabilitation programs accordingly. Therefore, once adjusted, VMO exercises done without the knee brace will not be in contradiction with functional exercises done with the knee brace.

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CHAPTER 2 REVIEW OF LITERATURE In the literature, there have been numerous studies conducted on the issue of Patellofemoral pain syndrome (PFPS). This topic is widely debated and there are many different views on the causative factors of PFPS. No consensus exists on a generic PFPS rehabilitation program. An overview of PFPS as well as a brief review of anatomy is needed for the purposes of this study. A review of the current literature concerning PFPS will reveal a need for more research in the area of rehabilitation. Patellofemoral Pain Syndrome Patellofemoral pain is the most frequent musculoskeletal disorder involving the knee seen in sports medicine clinics.3,44 Many studies have verified the prevalence of patellofemoral pain as the most common clinical condition presented to clinicians who treat musculoskeletal conditions.59 Patellofemoral pain was demonstrated by Deveraux and Lachmann12 to be the diagnoses of 25% of all knees evaluated in a sports injury clinic over a five year period. According to McConnell,34 patellofemoral pain affects one in four of the general population. In addition, the incidence of this disorder can also be seen in a study conducted by Finestone et al.18 in a military setting. Throughout 14 weeks of basic training 84 out of 395 knees were diagnosed as having overuse patellofemoral pain.18 This high incidence of patellofemoral pain seen in these studies encourages more extensive research on the topic so that a better understanding and consensus of treatment may be reached. 6

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7 The symptoms of PFPS are many and often vary from person to person in severity. The most common symptom in patients with PFPS is anterior knee pain. Pain is generally diffuse and arising from the anterior aspect of the knee along the medial aspect of the patella; however, lateral patella pain and retropatellar pain are also seen.44 This anterior knee pain often arises during and after physical activity that increases patellofemoral compressive forces. These activities include loading of the lower extremity in walking up and down stairs, squatting, and prolonged sitting with knees flexed.44,55 During an assessment of an athlete with patellofemoral pain the Patellar Grind Test is often positive and palpation of the medial and lateral borders of the patella cause pain.44 Some other symptoms that may be present include swelling, loss of motion, and a sensation of giving way or instability of the knee joint.44 Anatomy The knee joint is surrounded by many muscle complexes that work together providing lower extremity stability and locomotion The muscle complexes involved in knee motion are the quadriceps, hamstrings, pes anserine, and gastrocnemius/popliteus/plantaris. All of these muscles are involved in knee function and most have some role on patellar tracking. Many bones are also involved in this joint and they include the femur, patella, tibia and fibula. The patella is classified as a sesamoid bone and it is the largest in the human body. This sesamoid bone is located in the tendon of the quadriceps femoris muscle and is triangular in shape. The patella articulates between the two femoral condyles in the groove provided. The patella acts to increase the leverage of the tendon of the quadriceps femoris muscle, maintaining the position of the tendon when the knee is flexed, and protecting the knee joint. Patellar tracking within the groove is dependent upon the pull

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8 of the quadriceps muscles and patellar tendon, the shape of the patella, and the depth of the femoral condyles.2,57 The quadriceps muscles include vastus medialis (VM), vastus lateralis (VL), vastus intermedius (VI), and rectus femoris (RF). The VM originates on the medial linea aspera of the femur. The VM inserts into the tibial tuberosity via the quadriceps tendon, patella, and patellar tendon. This muscle serves to extend the knee as well as function as a major medial stabilizer for the patella.2 During knee extension the VM pulls the patella medially due to its orientation relative to the patella. The VM is angled at approximately 55 from the longitudinal axis of the femur aiding in medial patellar pull.44 The VL originates on the lateral linea aspera of the femur. It inserts into the tibial tuberosity via the patella and patellar tendon. The VL also functions to extend the knee. During knee movement and patellar tracking, the VL pulls laterally on the patella. The VI originates on the anterior and lateral surfaces of the body of the femur. This muscle also inserts on the tibial tuberosity via the patella and patellar tendon. The main function of this muscle is knee extension pulling the patella proximally and laterally.2,57 The RF muscle is the only two-jointed quadriceps muscle. It originates on the anterior inferior iliac spine, and attaches on the tibial tuberosity via the patella tendon. This muscle functions as a hip flexor as well as a knee extensor. During patellar tracking the RF muscle pulls the patella proximally and laterally.2,57 Contributing Factors of PFPS The source of patellofemoral pain has been in debate and cannot be sufficiently pinpointed. Authors suggest several possibilities as to the origin of PFPS described in detail in the following paragraphs.

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9 Several etiologies are mentioned by Brody and Thein7 in their review of nonoperative treatments for patellofemoral pain. Intrinsic and extrinsic factors include quadriceps insufficiency, hamstrings and iliotibial band inflexibility, lateral retinacular tightness, femoral anteversion, a wide pelvis, excessive pronation, knee ligament injury, acute trauma, instability, immobilization, and overuse.7,14,39 In a review of current PFPS issues Thomee et al.55 discusses three major contributing factors of PFPS. These factors include lower extremity and/or patellar malalignment, muscular imbalance, and overactivity. Another factor contributing to PFPS involves abnormal patellar tracking which may be caused by decreased VMO strength compared to the VL, or the firing rate of the VL before the VMO. Malalignment Lower extremity malalignment factors include femoral neck anteversion, genu valgum, knee hyperextension, quadriceps angle (Q-angle), tibia varum, and excessive rearfoot pronation.55 These malalignment factors are seen in people with patellofemoral pain, however these factors may also be seen in 60 to 80% of the normal population. This questions the use of the term malalignment.47 Patellar malalignment refers to the configuration of the trochlea and the inter-relationship between the patella and femoral surfaces.55 Muscular Imbalance Muscular imbalances associated with flexibility have been discussed as important factors contributing to knee pain. This is usually referred to as quadriceps or hamstring muscle tightness.55 This has also been demonstrated in decreased knee extensor strength in people with PFPS, but it is undetermined whether this decreased strength causes or is a result of PFPS.55 The muscular imbalance associated with firing sequence between the

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10 VMO and the VL has also been discussed. The VMO has been shown to have a slower reflex response time than the VL as measured by EMG.55 This type of imbalance may lead to patellar tracking problems. Patellar Tracking A commonly accepted cause of patellofemoral pain is related to abnormal patellar tracking within the trochlear groove which increases patellofemoral joint stress.44,25 Insall et al.,23 using radiographic examination, stated that patellar tracking abnormalities were the major cause of patellar pain. This abnormal patellar tracking and increased joint stress is believed to increase shearing and compression associated with articular cartilage wear and subsequent degeneration.45 The articular cartilage itself has been dismissed as a source of symptoms. It has been proposed that the subadjacent endplate is exposed to pressure variations that would normally be absorbed by healthy cartilage, and this pressure then stimulates pain receptors in the subchondral bone.20 This tracking problem is believed to be caused by a muscular imbalance of the dynamic stabilizers of the patella. This imbalance leads to excessive lateral forces in relation to the medially directed forces acting on the patella.25 This patellar tracking problem has often been conservatively treated by strengthening the dynamic stabilizers of the patella.22 These dynamic stabilizers include pes anserinus and semimembranosus muscles, biceps femoris, VM, VL, VI, and RF. The VMO has been implicated as being the primary medial stabilizer of the patella.44 Vastus Medialis Oblique The VMO has been identified as the distal fibers of the VM. Lieb and Perry30 stated that these distal fibers are angled approximately 55 from the longitudinal axis of the femur. This increased angle gives the VMO a mechanical advantage allowing the

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11 muscle to be proficient in preventing lateral patellar subluxation Consequently, the VMO has been thought to counterbalance the lateral pull of the larger VL to ensure patellar stability within the trochlear groove.30 The VMO is very important in this role, and according to some studies investigators have found differences in VMO and VL activity.52 These differences suggest that the lateral pull of the VL is not adequately counteracted by the medial pull of the VMO. This greater lateral pull results in lateral tracking and malalignment of the patella causing patellofemoral pain.43 VMO-VL firing rate differences have been thought to be another contributing factor to PFPS. In studies were the VMO had been thought to be weaker than the VL, authors suggest that the timing of the muscle contractions may also differ. The VL has been believed to contract before the VMO in concentric and eccentric quadriceps activity instead of simultaneously.43 This hypothesis has been supported by Voight and Wieder58, who found that activation of the VMO in subjects with patellofemoral pain was delayed as compared to the VL during a patellar tendon tap. Morrish and Woledge37 also reported a shorter reflex response time of the VL compared to the VMO in patients with patellofemoral pain. In contrast, normal individuals had significantly earlier VMO firing versus the VL in the same study. In contrast, a study conducted by Powers et al.43 found no timing or intensity differences between the VM and VL in patients with patellofemoral pain. Treatment for Patellofemoral Pain Operative Operative treatment for patellofemoral pain should always be a last resort, and only if nonoperative conservative treatments have been unsuccessful. These treatment methods are often directed at treating malalignment, extensor mechanism abnormalities

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12 or injured cartilage.55 Some of these operative treatments include lateral retinacular release, proximal realignment procedures, elevation of the tibial tubercle, anteromedial tibial tubercle transfer and elevation, articular cartilage procedures, and patellectomey.55 Non-operative Non-operative treatment of patellofemoral pain is always preferable to operative treatment. Every non-operative protocol should be exhausted before surgery is considered. A successful non-operative or conservative treatment first requires a thorough analysis of predisposing anatomical, physiological and lifestyle factors.7 Once these have been established the causative factor of the pain may be identified and corrected through a rehabilitation program. Conservative interventions include patient education, mobilization techniques, modalities, medications, acupuncture, quadriceps strengthening, taping, and bracing.5,7 These have also been used in combination to create a well rounded rehabilitation program.3,5,7 Patient education is very important with any injury and especially with patellofemoral pain. The patient must be informed on the contributing factors and the treatments available, therefore enabling them to modify and minimize possible causes of their pain. Patient education is also important for recurrent patellofemoral pain, so the patient may avoid exacerbating symptoms.7 Self-management becomes an important role in the long-term care of knee injuries. Patient education should come first in the management of patellofemoral pain followed by the chosen rehabilitation protocol. Mobilization techniques such as patellar manipulation and muscle stretching have been investigated as non-operative treatments of patellofemoral pain. Patellar mobilizations can be applied when soft tissue shortening produces an imbalance such as a lateral glide, tilt, or rotation of the patella.7 Rowlands et al.48 compared a group of

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13 patients who received a patellar mobilization procedure with a group that received detuned ultrasound. The patellar mobilization involved a manual sustained glide followed by high-velocity low-amplitude manipulation. The patellar mobilization group demonstrated significantly lower levels of pain than the control group at a 1-month follow-up, but no difference was found in functional outcome between groups.48 Muscle stretching techniques involve the lateral structures of the knee such as the iliotibial band, lateral retinacular tissues, and other surrounding muscular complexes such as the quadriceps, hamstrings, and gastrocnemius. Doucette and Goble13 studied patients with lateral patellar compression, and found that after an 8-week rehabilitation program the patients that were pain free had an improved Obers test and an improved congruence angle averaging 6.6. A study conducted by Smith et al.51 found a correlation between patellofemoral pain and poor hamstring and quadriceps flexibility. Tightness in the gastrocnemius muscle can contribute to patellofemoral pain by increasing dynamic pronation, which in turn increases patellofemoral joint reaction forces.7,15,27,50 The goal of modalities in the treatment of patellofemoral pain is to decrease pain. This is primarily achieved through the use of ice, however ultrasound, phonophoresis, and iontophoresis have also been used.1,7 Modalities such as electrical stimulation have been used to facilitate quadriceps muscle activity. Bohannon6 used VMO electrical stimulation to prevent patellar subluxation during a rehabilitation protocol. Electrical stimulation is helpful in muscle reeducation for individuals with acute pain, edema, or significant weakness who are unable to activate their quadriceps.7 Quadriceps strengthening Quadriceps strengthening is an important part of patellofemoral pain rehabilitation. A rehabilitation program often consists of a combination of quadriceps strengthening and

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14 another chosen non-operative treatment.7 The mechanism by which strengthening decreases patellofemoral pain symptoms and functional ability has not been established. The wide spread use of this method indicates its importance in the over all PFPS rehabilitation process. Natri et al.39 investigated factors that may predict long-term outcome in chronic PFPS. Forty-nine subjects with unilateral PFPS were enrolled in the study and underwent a 6-week conservative treatment protocol. The protocol consisted of rest, nonsteroidal anti-inflammatory medication, and intensive quadriceps strengthening exercises. A follow-up evaluation was performed at 6 months and 7 years post the 6-week protocol. The results of the study indicated that restoration of quadriceps strength and function to the affected extremity was important for long-term patient recovery. Witvrouw et al.61 investigated open kinetic chain (OKC) versus closed kinetic chain (CKC) exercises for patellofemoral pain. The subjects were divided into two groups and they either performed OKC or CKC exercise protocols. Each subject was evaluated with a subjective outcome assessment, functional outcome assessment, muscle-strength measurement, and muscle length measurement prior to 5 weeks into training, and 3 months after training. The CKC group had a few significantly better functional results for some of the tested parameters compared to the OKC group. However, after the protocols were completed both groups demonstrated a significant increase in overall functionality, as measured by the Kujala scale, and a decrease in pain. Therefore, the authors concluded that both OKC and CKC exercises lead to improved subjective and clinical outcome scores in patients with anterior knee pain.61

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15 Another study was conducted by Doucette and Goble13 to assess exercise on patellar tracking. Twenty-eight subjects and 56 knees diagnosed with lateral patellar compression syndrome were studied. The subjects participated in a five-stage rehabilitation program designed to meet each subjects specific needs using VMO exercises. These exercises included straight leg raises (SLR) with external rotation, squats, seated leg press, single knee dips, and others. Doucette and Goble13 found that patellar tracking was improved with VMO strengthening in lateral patellar compression syndrome. All of the above studies focused on quadriceps strengthening exercises to decrease PFPS symptoms. Strengthening with a patellofemoral brace was not studied in any of these studies. The exercises used to strengthen the quadriceps in a PFPS rehabilitation protocol need to be investigated while wearing a patellofemoral knee brace. Patellofemoral taping Patellofemoral taping is another method employed by rehabilitation specialists to treat PFPS. This technique was devised by McConnell and has been utilized to create a passive correction of lateral patellar tracking, tilt, and rotation.28 Studies investigating its ability to correct patellar alignment during quadriceps rehabilitation thereby decreasing pain associated with PFPS have been conducted.34,16 Other investigations include EMG activity of the quadriceps with and without patellar taping19,40 and patellofemoral taping used in combination with other treatments such as exercise and modalities mentioned above. Worrell et al.62 investigated the effect of patellar taping on patellar position as determined by magnetic resonance imaging (MRI) in patients with patellofemoral pain. Static MRI was used with the knee at eight different angles of knee flexion to determine

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16 the placement of the patella in the trochlear groove. Patellar placement was determined by digitization of patellofemoral congruence angle, lateral patellar displacement, and lateral patellar angle. The authors concluded that patellar taping influenced patellar position, produced less lateral patellofemoral congruence angle, and a more medial lateral patellar displacement, at 10 of knee flexion during the static MRI. Another study conducted by Kowall et al.28 also studied patellar taping in the treatment of patellofemoral pain. This study incorporated a control group utilizing a physical therapy program and a second group that underwent a physical therapy program combined with patellar taping. The activity of the VM and VL muscles were assessed during a CKC step-up and step-down exercise using surface electromyography (EMG) electrodes. Both groups experienced a statistically significant decrease in the frequency of pain, but no significant difference between the groups in their improvement as measured by a visual analog pain scale. The EMG activity of the symptomatic knees increased significantly from the beginning to the end of therapy for both groups, which was not seen in the asymptomatic knees. The increase in EMG activity was not significantly different between the two testing groups.28 Ernst et al.16 investigated knee kinetics with and without patellar tape in patients with PFPS. This study examined the effect of McConnell patellar taping on a single-leg vertical jump and lateral step-up. Maximal knee extensor moment, knee power, and vertical jump height were measured using a force platform and motion analysis system. The results indicated greater knee extensor moment and power with patellar taping than without.16

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17 The effect of patellar taping on pain and neuromuscular performance was studied in subjects with patellofemoral pain by Ng and Cheng40. The study was a pre-test post-test treatment design with the order of treatment randomized. Fifteen subjects performed a single leg stance with the stance leg in 30 of knee flexion and wearing a weight belt equivalent to 20% of their body weight, with and without the patellar tape. The results of the study indicated that patellar taping significantly decreased patellofemoral pain and VMO to VL EMG ratio. The VMO was found to be less active with the patellar tape and the researchers advised caution when taping and rehabilitation for PFPS are used together.40 This study indicated that further research is needed on this topic, possibly including patellofemoral bracing and EMG activity.These same results may occur with application of a patellofemoral brace which may undermine rehabilitation protocols, therefore further research is warranted. A similar study was conducted by Gilleard et al.19 on the effect of patellar taping on the onset of VMO and VL muscle activity in persons with patellofemoral pain. Fourteen female subjects with patellofemoral pain walked up and down stairs with and without patellar taping. The results indicated that taping of the patellofemoral joint changed the timing of the VMO and VL activity during step-up and step-downs in patients with patellofemoral pain. The onset of VMO activity in particular occurred earlier with patellar taping during both tasks.19 These conclusions are in contrast to the above study indicating that further research in the area of EMG activity and patellar realignment devices are needed. Patellofemoral bracing Patellar braces are designed to assist in correct tracking of the patella in the trochlear groove, to decrease pain, and prevent patellar subluxation or dislocation.42

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18 These patellar braces are normally constructed of neoprene material with or without a patellar relief hole in the sleeve over the patella. Felt, rubber, or gel inserts may be placed in positions above, below, medial, or lateral to the patella to limit and control patellar tracking as the knee extends.42 These braces may also include medial and lateral stays to provide stability to the brace and to prevent wrinkling of the elastic material.42 The use of patellofemoral bracing as a treatment technique and its effect on quadriceps muscle activity is what this study is focusing on. Many studies have been conducted advocating the use of a patellofemoral brace in either prevention or treatment of patellofemoral pain.4,31,49 A few studies indicated no significant relationship between bracing and patellar kinematics. Only one study had been found that investigated EMG activity of the VMO and VL with and without the use of a patellofemoral knee brace.21 These studies will be discussed to indicate the further need for more research. A study conducted by Worrell et al.62 investigated the effect of patellar taping and bracing (Palumbo Brace, DynOrthotics LP, Vienna, VA) on patellar position as determined by MRI in patients with patellofemoral pain.62 During the study, static MRI images were taken at 8 different angles of knee flexion. It was concluded that patellar bracing and taping influenced patellar position at 10 of knee flexion during a static MRI condition. The researchers also agree that more investigation is needed to determine etiological factors and long-term outcomes of conservative and surgical treatment.62 Shellock et al.49 were involved with a case study to determine the effect of applying a newly developed patellar realignment brace to a patient with lateral subluxation of the patella. The brace had a viscoelastic silicone insert with a guide designed to counteract patellar subluxation. MRI information taken during active movement indicated that the

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19 brace corrected the lateral displacement of the patella. The patient involved in the study also underwent physical rehabilitation and had no painful symptoms 4 months later.49 This was a case study involving only one subject; therefore, more research is needed with additional subject participation to determine the effect of the patellar realignment brace. Another research team, BenGal et al.4 investigated the role of the knee brace in prevention of anterior knee pain. The knee brace incorporated a silicon patellar support ring and was worn by 27 subjects (21 men, 6 women), who had no previous history of anterior knee pain, while performing increasingly intensive exertion exercises. As the exercise intensity increased, anterior knee pain syndrome appeared more frequently. Male athletes wearing the braces before the exercise sessions had significantly less incidence of PFPS than those that did not wear the brace. The researchers concluded use of the knee brace may be an effective way to prevent anterior knee pain in people performing intensive physical activity.4 More intensive investigation needs to be completed regarding this subject, feasibility prevents everyone participating in intensive physical exercise from wearing a knee brace. A look at what the knee brace is accomplishing while being worn needs to be investigated. Another investigation was done on the patellar brace to assess its effect on performance in a knee extension strength test in patients with patellar pain.31 Lyshom et al.31 used a Cybex-II to test strength performance with and without the brace in 24 patients with patellofemoral arthralgia. Twenty-one patients improved their performance in the strength test with the brace than without the brace. Fourteen patients performed at least 95% of their control leg strength while wearing the brace. The researchers concluded that the results support the use of this brace in conservative management of

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20 patients with patellofemoral arthralgias.31 The researchers in this study also advocate the use of a brace as a supplement in a quadriceps rehabilitation program to improve the effect of the training.31 The activity of the quadriceps needs to be examined while wearing the patellar brace to determine if this supplementation during quadriceps rehabilitation is appropriate. Contrary to the above studies, Muhle et al.38 found no stabilizing effect of the tested brace in patients with patellar subluxation or dislocation during active joint motion. Muhle et al.38 examined 21 patients with clinical evidence of patellar subluxation or dislocation with kinematic MRI with and without a patellar realignment brace. The researchers found no statistically significant differences in the patellofemoral relationships before or after wearing the patellar brace. The study conducted by Powers et al.45 indicated similar results concerning the effect of bracing on patellar kinematics in patients with patellofemoral joint pain. Kinematic MRI of the patellofemoral joint was taken through the ranges of 45 to 0 of knee flexion with and without a patellofemoral joint brace. The results indicated no statistically significant difference between the braced and unbraced trials. One study was done concerning patellar bracing and its effect on quadriceps EMG activity. This study was conducted by Gulling et al.21 on 16 athletically active individuals who were all concurrently participating in physical therapy. All subjects demonstrated symptoms indicative of PFPS but had no history of knee surgery or traumatic knee ligamentous injury. Each subject was then tested on an isokinetic dynamometer (Kin-Com) with and without the patellofemoral brace (U1004-patellar stabilizer). Surface EMG activity was recorded from the VMO and VL during three

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21 maximal concentric/eccentric quadriceps contractions at an angular velocity of 180/second. The EMG data indicated that the application of the patellar brace produced significantly smaller IEMG (integrated EMG) signals than the non-braced condition in both muscles and both contractions.21 The IEMG data were also significantly greater for the VMO than the VL in both conditions, and during the concentric muscle contraction compared to the eccentric muscle contraction. The results demonstrate that patellar bracing may lower neuromuscular activation of the quadriceps muscles during isokinetic knee extension. The researchers suggested this decrease of IEMG activity was a contribution in the reduction of symptoms of PFPS. By reducing stronger muscle contractions lateral patellar tracking may incidentally be reduced also.21 This study was conducted with only an OKC exercise. Similar investigations conducted with CKC are needed. Additionally, a study on a non-injured population would give researchers a better idea of the patellar braces effect on quadriceps activity. Further investigation is warranted to support or refute the findings of this study. Electromyography Surface EMG has been used in research to detect muscle activation. More specifically surface EMG has been used in studies when the activity of the quadriceps muscles was collected.19,24,29,33,40 There are many considerations that must be addressed when surface EMG is utilized. A differential electrode configuration should be used with surface EMG. This configuration relates to the detection surface of the EMG electrode. This detection surface should consist of two parallel bars, both 1.0 cm long, 1-2mm wide, and 1.0 cm apart. A bandwidth of 20-500 Hz should be used with a roll-off of at least 12dB/octave,

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22 and a common mode rejection ratio of >80dB. The noise should be <2uV rms (20-400 Hz) and an input impedance > 100 meg ohms.11 The two electrodes should be placed on the midline of the muscle belly to receive the best signal. The electrodes on the midline of the muscle belly need to be between the myotendinous junction and the nearest innervation zone. The detection surfaces should be oriented perpendicular to the length of the muscle fibers.11 Gulling et al.21 conducted a study on the effects of patellar bracing on quadriceps EMG activity during isokinetic exercise. The EMG electrodes were placed in the centers of the VMO and VL muscle bellies along the longitudinal axis of the muscle fibers and the centers of the electrodes were placed 3.0 cm apart. The two ground electrodes were placed over the medial and lateral malleoli. Raw EMG signals were collected at a sampling frequency of 1000 Hz, pre-amplified at a 1,000,000:1 gain, and processed through an analog to digital (AD) conversion. This rectified EMG activity was then integrated and stored on an IBM microprocessor and analyzed over the 10-35 degree arc of motion.21 This type of EMG set-up is similar to the process that will be utilized in the current study. Ng and Cheng40 used a similar set up in a study investigating the effects of patellar taping on pain and neuromuscular performance in subjects with PFPS. Two pairs of Ag/Ag Cl surface electrodes with a diameter of 1 cm were used to record the EMG muscle activity of the VMO and VL. These electrodes were placed over the mid-point of both muscles along the muscle fiber directions. Each electrode on the same muscle was separated by 2.5 cm. The electrodes were attached to an input box and an amplifier that performed linear enveloping between 15-1000 Hz and a differential amplification of

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23 1000x. The common mode rejection ratio (CMRR) of the amplifier was 80dB. The rectified full wave signal was input into an AD converter, which sampled at 2500 Hz and the digitized signals were sent to a personal computer with Global Lab software for analysis.40 Lam and Ng29 investigated the activation of the quadriceps muscle during semisquatting with different hip and knee positions in patients with anterior knee pain. This study did not apply patellofemoral tape or a brace during the exercises. Active surface electrodes with a built-in gain of 1000x and a band pass filter of 20-450 Hz were applied along the fiber direction of the muscles to detect muscle signals. Raw EMG signals were input into a data acquisition unit that performed AD conversions at a sampling frequency of 500 Hz. This digitized EMG data were then integrated over time and output to a personal computer for display and storage.29 The above studies used similar EMG parameters to determine muscle activation. These parameters varied depending on the type of software that was utilized for each individual study. Many of these parameters seen in the above studies will be utilized in the current study and will vary according to the software utilized.

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CHAPTER 3 METHODS The goal of this study was to gain information that would help in the development of rehabilitation protocols for patellofemoral pain. These protocols may change to benefit the athlete with a greater understanding of muscle function when performing these exercises with and without the patellar stabilizing brace. To accomplish this we utilized a within subject repeated measures design. Subjects Twenty-three healthy subjects from the University of Floridas student body were recruited for this investigation. The subjects were between the ages of 18 and 30 years and did not have a history of any lower extremity injury. The subjects were also resistance trained and familiar with the knee extension and leg press exercise. Prior to participating, each subject read and signed an informed consent agreement approved by the universitys Institutional Review Board. Instrumentation Electromyography (EMG) A Myopac EMG system (Run Technologies, Laguna Hills, CA) was used to collect the raw EMG signal. The unit specifications for the EMG included a frequency bandwidth of 10-1000 Hz, CMRR of 110 dB, input resistance of 1 M, and a sampling rate of 2000 Hz. Following sampling, EMG data underwent an AD conversion and was stored on a PC-type computer using the DATAPAC 2000 (Run Technologies, Laguna Hills, CA) analogue data acquisition, processing, and analysis system. 24

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25 Patellofemoral Knee Brace The Patella Stabilizer with Universal Buttress by Meller was utilized for this study. This knee brace is secured to the leg by two Velcro straps, one below and one above the patella. Four different sizes (S, M, L, XL) were available for use by the subjects depending on the manufactures specifications of each subjects knee and calf girth. Measurements One Repetition Maximum (1-RM) The 1-RM test followed light cycling on a stationary cycle for 3 minutes and a warm-up set of 10 repetitions using low resistance (approximately 10% of body weight for the knee extension and 50% of body weight for the leg press). The 1-RM test for the knee extension exercise was assessed first, followed by the leg press. A five-minute recovery period was taken between exercises. For both exercises the weight was progressively increased (2.2kg for the knee extension and 4.4kg for the leg press) until the subject could no longer complete the concentric phase of the lift unassisted. The maximal weight the subject was able to lift concentrically unassisted was used as the 1-RM Muscle Activity Quadriceps muscle activity of the dominant leg during open kinetic chain (OKC) and closed kinetic chain (CKC) knee extension was determined from the amplitude of the EMG signal. To begin this procedure, each subjects skin was shaved and cleaned with isopropyl alcohol to reduce skin impedance. Immediately following, bipolar 1-cm Ag/AgCl surface electrodes were placed parallel with the muscle fibers at a point midway between the motor point and the musculotendinous junction of the vastus medialis (VM)

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26 and vastus lateralis (VL) using an inter-electrode distance of 1.5-cm. The electrode placements were confirmed with manual muscle testing and checked for cross-talk with real time oscilloscope displays. After placement was confirmed, the maximal EMG activity of both muscles were measured and recorded during a 1-RM lift on the leg press and the leg extension machine. After a brief rest period, muscle activity was recorded during the concentric and eccentric phases of each exercise, which was done at 75% of the subjects 1-RM. The first 45 and the second 45 of both the concentric and eccentric phases of each exercise were marked on the EMG with a manual switch controlled by the researcher. This manual switch was activated at the start of the concentric phase and released on the eccentric phase to distinguish the different contractions from each other on the EMG signal. The acquired raw signals were digitally processed using a symmetric root mean square (RMS) algorithm, with a 10-msec time constant. All muscle activity recorded during testing was expressed as a percentage of the normalization base (% 1-RM). Procedures Each subject reported to the Athletic Training/Sports Medicine Research Laboratory on two separate occasions. During the first session, each subject was assessed for his or her 1-RMon the leg extension and leg press exercises. When the 1-RM testing was completed the session was over and the subject was free to leave. The subjects returned for the second session after a period of at least 48-hrs following the first session. During this session, each subject was assessed for quadriceps activity while performing both the knee extension and leg press exercises. For each exercise the resistance used was equivalent to 75% of the previously determined 1-RM. The subjects were also assessed under two conditions during these exercises; braced and

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27 unbraced. During the braced condition, each subject wore a patellar stabilizing brace on the dominant leg. The brace was fitted according to the manufacturers specifications and based on the circumference of the knee and calf. The order of the four conditions; OKC braced, OKC unbraced, CKC braced, and CKC unbraced were randomly assigned and counterbalanced. A five-minute recovery period separated each condition. After the 1-RM was done on the second day for normalization of the EMG, the knee extension and leg press exercises were performed. Five repetitions of each exercise were performed and the measurement took place during both the concentric and eccentric phases. A switch controlled by the researcher distinguished the concentric phase from the eccentric phase. A metronome was used to control for the rate of movement, which consisted of a three-second concentric and a three-second eccentric phase. When all four conditions were completed the session was over and the subject was free to leave. Data Analysis SPSS 11.0 for Windows (SPSS, Inc., Chicago, IL) was used for statistical analysis. Two repeated-measures ANOVAs with three within-subject factors were used to analyze the data. The three factors were exercise (OKC, CKC), treatment(braced, unbraced), phase of exercise (first and final 45 concentrically, first and final 45 eccentrically). An ANOVA was completed for each muscle (VM, VL). Tukeys HSD Post hoc analyses were used to locate the differences of interest if significant interactions resulted from the ANOVAs. An alpha level of p < .05 was set a priori for all statistical analyses.

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CHAPTER 4 RESULTS The purpose of this study was to examine the effects of a patellofemoral knee brace on quadriceps muscle activity during open kinetic chain (OKC) and closed kinetic chain (CKC) knee extension exercises. Male and female college-age subjects were recruited for this study. Each subject performed OKC and CKC chain exercises with and without a brace in a randomly assigned order. Quadriceps electromyographic (EMG) activity was recorded for each condition. Subject Demographics Twelve male and 11 female students from the University of Florida participated in this study. All of the subjects were healthy and had no history of previous knee injury. Subject demographic data are presented in Table 4.1. Table 4.1 Subject demographics (means SD). Subjects Age (y) Height (cm) Weight (kg) N = 23 232.71 171.066.96 68.9112.17 Vastus Medialis The ANOVA for vastus medialis (VM) EMG activity did not reveal a significant interaction between the type of exercise, the braced condition, and the phase of exercise [F(3,92)=0.772, p=0.514]. It also failed to reveal a significant interaction between the type of exercise and the braced condition [F(1,92)=3.417, p=0.078]. However, a significant interaction between the type of exercise and the phase of exercise [F(3,46)=59.67, p=0.000] 28

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29 was revealed. The Tukey HSD post hoc analysis determined that differences of 4.44% or greater were considered significant (Table 4.2). Table 4.2. Normalized VM activity during OKC and CKC knee extension (Mean SD) Concentric Eccentric Exercise 90 to 45 45 to 0 0 to 45 45 to 90 OKC 90.04.4% 78.84.4% 60.53.6% 68.83.3% CKC 84.04.8% 44.43.8% 59.83.8% 93.64.8% Significantly greater than CKC during same phase of exercise (p<.05). Significantly greater than OKC during same phase of exercise (p<.05). A statistically significant interaction was also observed between the braced condition and the phase of exercise [F(3,46)=4.917, p=0.004]. The Tukey HSD post hoc analysis determined that differences of 4.44% or greater were considered significant (Table 4.3). Table 4.3. Normalized VM activity during braced and unbraced conditions (Mean SD) Concentric Eccentric Exercise 90 to 45 45 to 0 0 to 45 45 to 90 Braced 91.4.0% 62.0.1% 62.9.8% 85.9.9% Unbraced 82.63.2% 61.22.7% 57.42.6% 76.62.5% Significantly greater than unbraced during same phase of exercise (p<.05). The ANOVA for the VM revealed no significant main effect for exercise type [F(1,23)=.836, p=0.371], suggesting no difference in EMG activity between OKC and CKC knee extension. However, significant main effects for braced condition [F(1,23)=5.082, p=0.034] and phase of exercise [F(3,92)=67.075, p=0.000] were observed. The normalized EMG activity when the knee brace was used (75.5 .9%) was significantly higher than when it was not used (69.4 .3%). The Tukey HSD post hoc analysis for the phase of exercise determined that differences of 3.4% or greater were considered significant. Therefore, the normalized EMG activity when the VM was contracting eccentrically from 45 to 90 of flexion (81.2 .0%) was significantly

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30 greater than when it was contracting eccentrically from full extension to 45 of flexion (60.1 .0%), and when it was contracting concentrically from 45 of flexion to full extension (61.6 .1%). However, the normalized EMG activity during the same phase of exercise was significantly lower than when the VM was contracting concentrically from 90 to 45 of flexion (87.0 .8%). Vastus Lateralis The ANOVA for vastus lateralis (VL) EMG activity did not reveal a significant interaction between the type of exercise, the braced condition, and the phase of exercise [F(3,46)=0.750, p=0.526]. It also failed to reveal significant interactions between the type of exercise and the braced condition [F(1,92)=.024, P=.879] and between the braced condition and the phase of exercise [F(3,46)=0.750, p=0.526]. However, a significant interaction between the type of exercise and the phase of exercise [F(3,46)=75.20, p=0.000] was revealed. The Tukey HSD post hoc analysis determined that differences of 4.44% or greater were considered significant (Table 4.4). Table 4.4. Normalized VL activity during OKC and CKC knee extension (Mean SD) Concentric Eccentric Exercise 90 to 45 45 to 0 0 to 45 45 to 90 OKC 86.9.3% 86.7.2% 66.0.2% 66.3.2% CKC 74.52.9% 40.72.9% 54.62.6% 82.83.3% Significantly greater than CKC during same phase of exercise (p<.05). Significantly greater than OKC during same phase of exercise (p<.05). The ANOVA for the VL revealed no significant main effect for the braced condition [F(1,23)=1.128, P=0.300]. However, significant main effects for the type of exercise [F(1,23)=.9.756, P=0.005] and the phase of exercise [F(3,92)=43.778, p=0.000] were revealed The normalized EMG activity of the VL was greater during OKC exercise

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31 (76.5 .7%) as compared to CKC exercise (63.2 .5%). The Tukey HSD post hoc analysis determined that differences of 3.40% or greater were considered significant. The normalized EMG activity when the VL was contracting eccentrically from 45 to 90 of flexion (74.6 .8%) was significantly greater than when it was contracting eccentrically from full extension to 45 of flexion (60.3 .9%), and when it was contracting concentrically from 45 of flexion to full extension (63.7 .6%). Also, the normalized EMG activity was significantly greater when the VL was contracting concentrically from 90 to 45 of flexion (80.7 .3%) as compared to all other phases of the knee extension exercises.

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CHAPTER 5 DISCUSSION The primary goal of this investigation was to determine if a patellofemoral knee brace would alter quadriceps activity during open kinetic chain (OKC) and closed kinetic chain (CKC) knee extension exercises. To accomplish this we examined 23 subjects without a history of knee pain. Quadricep electromyographic (EMG) activity of the vastus medialis (VM) and vastus lateralis (VL) were obtained from each subject while they performed OKC and CKC exercises with and without a knee brace. Two ANOVAs were utilized to analyze the data collected. Vastus Medialis We initially hypothesized that VM activity would be reduced when the subjects wore the knee brace compared to when they did not. We further hypothesized that this would occur regardless of the type of exercise (OKC versus CKC). However, this did not occur, as VM activity during both the OKC and CKC exercises increased when the knee brace was worn. Specifically, when the data from both exercises and each phase of exercise were pooled together, the VM activity was actually greater during the braced condition. When separated by phase of exercise, the braced conditions resulted in greater activity both concentrically and eccentrically when the knee was in the more flexed phase. Bracing had no effect on VM activity during the final 45 of knee extension. VM activity was greatest when the muscle was contracting concentrically from 45 of flexion to full extension. This was not affected by the knee brace. When the type of exercise was compared, VM activity during this phase was significantly greater in the 32

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33 OKC compared to the CKC. However, when the VM was contracting eccentrically from 45 to 90 of flexion, the activity was greater in the CKC. Vastus Lateralis Like the VM, we initially hypothesized that VL activity would be reduced when the subjects wore the knee brace compared to when they did not. We further hypothesized that this would occur regardless of the type of exercise (OKC versus CKC). However, this did not occur, as no differences were observed between the braced and unbraced conditions when comparing the VL activity during both the OKC and CKC exercises. Unlike the VM, the greatest VL activity occurred when the knee was extending from 90 to 45 of flexion. When the type of exercise was compared, VL activity was greatest during the OKC exercise. This was observed during the final 45 of extension concentrically and eccentrically. However, when the knee was in a more flexed position the eccentric activity was greater during the CKC exercise. Patellofemoral Bracing The concept behind the present study was similar to a study conducted by Gulling et al21 that investigated the effect of patellar bracing on quadriceps EMG activity during isokinetic exercise. However, the results of the present study are in contrast to their results. Gulling et al.21 reported significantly greater EMG readings in subjects performing isokinetic exercises during a non-braced condition versus a braced condition. In the present study, we observed significantly greater quadriceps EMG activity when the patellar brace was worn (Figure 5-1).

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34 VM00.20.40.60.811.21.41.6Braced ConditionEMG Unbraced Braced Figure 5-1. VM EMG activity during braced conditionsignificantly greater than the Unbraced Condition (P 0.05) The significant decrease in quadriceps EMG activity after the application of the brace was thought by Gulling et al21 to induce a weaker muscle contraction reducing abnormal patellar tracking and decreasing symptoms of patellofemoral pain syndrome (PFPS). The conflicting results may be attributed to the type of subjects and the exercise protocol utilized in each study. Gulling et al.21 used subjects who were suffering from patellofemoral pain at the time of the study and they performed only an isokinetic OKC exercise protocol. In the present study, only healthy subjects were used and they completed both an OKC exercise (knee extension) and a CKC exercise (leg press) protocol. Healthy subjects were chosen to examine if the application of the brace would have a similar effect on the quadricep muscle activity of individuals without patellofemoral pain. The results may suggest that healthy subjects respond differently to the patellofemoral brace application compared to subjects with patellofemoral pain. The CKC exercise (leg press) was used to incorporate a functional aspect, and a CKC exercise (knee extension ) was used to assess the efficacy of a frequently used rehabilitation tool.

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35 These exercises are very different from an isokinetic exercise. It is possible that the fixed speed with the isokinetic exercise may have produced different EMG readings seen in the Gulling et al.21 study. A metronome was utilized in the current study in an attempt to control for speed alterations during the exercise. The subjects in the existing study may have deviated slightly from the constant speed that was set by the metronome, therefore producing different results. In addition, the brace applied pressure on the EMG surface electrodes, which may have caused higher EMG activity readings during the braced condition compared to the non-braced condition. Gel from the surface electrodes was observed around the area after brace application, which may suggest more topical pressure on the electrodes compared to the non-braced condition. This possible limitation was not noted in the study conducted by Gulling et al.21 The inability to allocate an accommodation period to the patellofemoral knee brace has been mentioned as a limitation in the present study. The previous studies that examined the effects of knee bracing on muscle activation also failed to examine the idea of an accommodation period.21,41 It is possible that muscle activation was affected by the application of the knee brace, which was not controlled for through an accommodation period. A previous study by Osternig and Robertson41 examined the effects of prophylactic knee bracing on lower extremity joint position and muscle activation during running. The results of this study revealed a significant reduction of EMG activity in73% of the subjects with the braced condition compared to the non-braced condition. The results of this study were also in contrast with the present study. Unlike the present study, Osternig and Robertson41 used a knee brace with a polyaxial hinge instead of a patella stabilizing brace. They also utilized a running protocol instead of a CKC and OKC exercise

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36 protocol. In both studies EMG activity was assessed. The running protocol was completed on a treadmill, possibly producing different EMG activity patterns compared to the leg press and knee extension exercise done in the present study. The leg press and the knee extension exercises were done at 75% of the subjects 1-RM. It is likely that this would produce an overall higher EMG readings, resulting in the differences found between the studies. In addition to the differences stated, Osternig and Robertson41 incorporated only 6 subjects in their study. This limited number may have affected the statistical significance that was seen during the braced condition. The present study included 23 subjects who all performed both exercises with and without the patellofemoral brace. The adequate number of subjects increases the statistical power of the present study reinforcing the significant differences found. Patellofemoral Taping Another treatment often incorporated in a rehabilitation protocol for patellofemoral pain is patellofemoral taping. The studies conducted on this treatment can be compared to the investigations mentioned above as well as the present study, because of the mechanisms that influence patellar tracking. Both the patellar brace and patellar taping attempt to aid the patella in proper tracking through the trochlear groove. Kowall et al.28 studied patellar taping in the treatment of patellofemoral pain. VM and VL activity was assessed during a CKC step-up and step-down exercise using surface EMG electrodes. This study revealed an increase in EMG activity over time during a rehabilitation program that utilized patellar taping.28 The results of this study would be similar to the present study if the increase in EMG activity was seen immediately after the patellar tape was applied. The change in the EMG activity seen by Kowall et al.28 was not noted until later in the rehabilitation protocol, which limits the comparison that

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37 can be made to the present study. The effect of patellar taping on pain and neuromuscular performance was studied in subjects with patellofemoral pain by Ng and Cheng.40 Their results indicated that patellar taping significantly decreased patellofemoral pain and VMO to VL EMG ratio. The VMO was found to be less active with the patellar tape, which is in contrast to the results of the current study.40 Unlike the present study, Ng and Cheng40 used subjects that presented with patellofemoral pain. The subjects used in the current study had no history of previous knee pain. The major difference between patellofemoral taping and patellofemoral bracing that needs to be considered is the placement of the device on the skin. The patellofemoral tape is normally based on the McConnell34 taping technique. This technique involves the application of tape only over the patella to aid in patellar tracking through the trochlear groove. Patellofemoral bracing encompasses the entire knee area, leaving the patella free, with a buttress surrounding the patella to aid in patellar tracking. The pressure of the brace on the quadricep muscle group may explain the increased EMG activity found with brace application in the present study. This increase in pressure caused by the patellofemoral brace is not seen with the use of patellofemoral taping. Exercise Comparison The results observed regarding the phase of exercise and exercise type are important to note although these results did not directly relate to the hypotheses of the present study. Unlike the previous studies mentioned, the results of the present study were very similar to results found in studies that investigated OKC and CKC exercises with EMG. A recent study done by Clements et al9 compared quadriceps EMG activity during OKC and CKC exercises. The EMG activity was collected during an isometric contraction using the leg press and the knee extension machine at 30, 60, and 90 of

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38 flexion. The results revealed that the OKC exercise had significantly higher EMG activity at 30 of knee flexion when compared to the CKC exercise at 30. The current study revealed similar results as the second phase of the concentric contraction (45 to 0 of knee flexion) was significantly greater in the OKC compared to the CKC (Figure 5-2). However, the second phase of the eccentric contraction (45 to 90 of knee flexion) was significantly greater in the CKC as compared to the OKC in the present study (Figure 5-3). Similar to these findings, Clements et al.9 reported significantly higher EMG activity in the CKC exercises at 60 and 90 of knee flexion compared to the OKC exercises in the same ranges. The results for the present study were reported regardless of the braced condition. A knee brace was not used in the Clements et al.9 investigation. Con 45 to 0 degrees of knee flexion00.10.20.30.40.50.60.70.80.912Exersice TypeEMG (mV) OKC CKC Figure 5-2. Concentric 45 to 0 of knee flexion during CKC and OKC exercises significant interaction (P 0.05)

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39 Ecc 45 to 90 degrees of knee flexion00.20.40.60.811.212Exercise TypeEMG (mV) CKC OKC Figure 5-3. Eccentric 45 to 90 of knee flexion during CKC and OKC exercises significant interaction (P 0.05) Escamilla et al.17 also conducted a study that revealed comparable results to the present study. The OKC exercises produced significantly greater quadriceps EMG activity between 15-65 of knee flexion and the CKC exercises produced significantly greater quadriceps EMG activity at knee angles greater than 83. These results are similar to the current study as well as the study conducted by Clements et al.9. The similarities among the studies are important to mention. Although the present study produced different EMG activity than previous studies that investigated patellofemoral bracing, the basic muscle activity of the quadriceps has been seen in multiple earlier studies. The results regarding the phase of exercise are also important to notice. The ANOVAs for both the VM and VL revealed significant interactions between phase of exercise. The EMG activity for the VM was greater during the concentric phase of motion, compared to the eccentric phase. However, the difference was not statistically

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40 significant. The EMG activity during the VLs concentric phase of motion was significantly greater than the eccentric phase. These results can be compared to a study conducted by Kellis and Baltzopoulos26 on muscle activation differences between eccentric and concentric isokinetic exercise. The results of this study revealed greater EMG activity during the concentric motion compared to the eccentric motion. Kellis and Baltzopoulos26 used an isokinetic dynamometer without a knee brace, whereas the present study utilized the knee extension and leg press machines with and without a patellofemoral knee brace. In the present study, the results for the phase of motion were reported in combination of both the braced and non-braced conditions. Although the study protocols were different they produced similar EMG activity readings for the VM and VL. Clinical Implications Many studies have verified the prevalence of patellofemoral pain as the most common clinical condition presented to clinicians who treat musculoskeletal conditions.59 The exact cause of this syndrome is not clear, and varies from patient to patient. The present study was an investigation into one of the many methods used to treat patellofemoral pain. The results of this study suggest that quadriceps muscle activation increases with the application of a patellofemoral knee brace. These results would support the use of a patellofemoral brace during a rehabilitation protocol for patellofemoral pain. However, it is important to be aware of the circumstances of the study protocol. Only healthy subjects who had no previous history of knee pain participated in the study, therefore subjects who have patellofemoral pain may respond differently to the knee brace as suggested by Gulling et al.21 The conflicting results between the current study and the

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41 study conducted by Gulling et al.21 suggests that rehabilitation specialists treat with caution when utilizing a knee brace as part of a rehabilitation protocol. Although a significant interaction was not revealed between the type of exercise, the braced condition, and the phase of exercise, it is important to note that the results did follow the trend observed in previous studies. Summary Patellofemoral pain is the most frequent musculoskeletal disorder involving the knee seen in sports medicine clinics.3,44 The prevalence of this syndrome has lead to extensive research in the area of rehabilitation. Many studies have been conducted advocating the use of a patellofemoral brace in either prevention or treatment of patellofemoral pain.4,31,49 Of the studies conducted on patellofemoral bracing, only one investigated the effect of the brace on quadriceps muscle activation.21 The purpose of the present study was to assess the effect of a patellofemoral knee brace on quadriceps muscle action. Twenty-three subjects with no previous history of knee pain were utilized in the current study to evaluate a healthy subjects response to a patellofemoral brace. Each subject performed OKC and CKC exercises with and without a patellofemoral knee brace. Surface EMG was utilized to assess quadriceps muscle activity during each exercise and braced condition. The data were analyzed to identify interactions. The data analysis demonstrated a significant increase in EMG activity of the quadriceps when the patellofemoral brace was applied, regardless of the exercise type. The results did not indicate a significant interaction between the type of exercise, the braced condition, and the phase of exercise. These results indicated that when the type of exercise is considered, OKC and CKC, there is no significant difference in the braced and

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42 unbraced conditions. The results of this study and the conflicting conclusions to the Gulling et al.21 investigation call for more extensive research on patellofemoral bracing and the effect of the brace on quadriceps muscle activity. Implications for Future Research The results of this study suggest a need for future research in the area of patellofemoral bracing. This study is the first known study to investigate patellofemoral bracing on quadriceps activity during OKC and CKC exercises. Previous investigations studied subjects with patellofemoral pain using an isokinetic dynamometer.21 It is evident that a more extensive investigation is needed into the effects of a patellofemoral knee brace on quadriceps muscle activity. Future research should consider subjects with and without patellofemoral pain as well as OKC and CKC exercise protocols. This would allow a comparison to be made between the patellofemoral pain group and the non-injured group. Future studies examining the effect of patellofemoral bracing on quadriceps activity should consider an accommodation period for the patellofemoral brace. This accommodation period would control for any immediate muscle activation differences that may be present with brace application. This added control may allow for more reliable results. Another aspect that may be considered during future investigations is the use of fine wire EMG. Fine wire EMG would decrease the effect that the surface EMG may have had on the results of the present study. The pressure applied to the surface EMG electrodes with the brace application may be eliminated with the use of fine wire EMG, therefore adding to the validity of the results.

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APPENDIX A UNIVERSITY OF FLORIDA INSTITUTIONAL REVIEW BOARD 1. TITLE OF PROTOCOL: The effect of a patellofemoral knee brace on quadriceps activity. 2. PRINCIPAL INVESTIGATOR: Madelon C. Haskin, ATC-L 2502 NW 16th Avenue Gainesville, FL 32605 Home: (352) 378-1337 Cell: (352) 235-0101 haskin02@hotmail.com 3. SUPERVISORS Dr. Michael Powers, Ph.D., Assistant Professor, Athletic Training University of Florida 144 Florida Gym P.O. Box 118205 (352) 392-0580 ext. 1332 mpowers@hhp.ufl.edu 4. DATES OF PROPOSED PROTOCOL: From February 15, 2003 to February 15, 2004 5. SOURCE OF FUNDING FOR THE PROTOCOL: Unfunded 43

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44 6. SCIENTIFIC PURPOSE OF THE INVESTIGATION: Patellofemoral pain is a common phenomenon in the physically active, and the patellofemoral knee brace is frequently advocated in rehabilitation protocols. The effect of the knee brace on the activation of the quadriceps muscles has not been thoroughly researched. This study may give professionals in the field of rehabilitation a better understanding of what is happening when their athlete applies a patellofemoral knee brace. This study will attempt to add to this knowledge base, thereby assisting rehabilitation specialists in precise programs to allow athletes to return to activity faster and with better long-term results. 7. DESCRIBE THE RESEARCH METHODOLOGY IN NON-TECHNICAL LANGUAGE: The purpose and procedures of the study will be explained to each subject and they will be asked to read and sign an Informed Consent. Once the forms have been completed and consent is given, the subjects will have their one repetition maximum assessed for the leg extension and leg press exercises. This involves beginning with a very lightweight for each exercise and progressing until a weight is reached that cannot be lifted one time. We will be using the protocol recommended by the National Strength and Conditioning Association. The subjects will then be asked to return at least 48 hours after their first day and will have one spot on their medial quadriceps (VMO) and one spot on their lateral quadriceps (VL) cleaned with isopropyl rubbing alcohol and any hair in those two places shaved off. Surface electromyography electrodes will be placed on these two areas to record muscle activity of the quadriceps muscles. Prior to performing the next tasks, the subject will warm up for 3 minutes on an exercise bike. The subjects will then perform one maximal effort for each exercise using the maximum weight obtained from the first session. The EMG measurements collected by this contraction will be used to normalize the data of the other exercises. Once this is complete the subject will then perform five repetitions of each exercise using 85% of the maximum weight obtained from session one. Each exercise will be performed twice, once while wearing a patellofemoral knee brace and again without the patellofemoral knee brace. The order of the exercises and the order of bracing (or not) will be randomly assigned. Quadriceps muscle activity will be recorded during the 5 repetitions of each exercise performed by the subject. There will be 5 minutes of rest between each testing condition. Measurements of subjects performances on all the tasks will be coded and analyzed in an anonymous fashion to maintain subject confidentiality. 8. POTENTIAL BENEFITS AND ANTICIPATED RISK The data collected may not directly benefit the subjects involved in the study. The study may ultimately benefit people with patellofemoral pain by facilitating a faster return to activity. Subjects performing some of the tasks for the first time may be at risk of injury due to unfamiliarity of the tasks or equipment. Consistently following proper set-up procedures and performing several practice trials for each task should minimize this risk.

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45 A National Athletic Trainers Association licensed athletic trainer (ATC/L) who will assess and treat any injuries that may occur will be present for all exercise and testing sessions. 9. DESCRIBE HOW PARTICIPANTS WILL BE RECRUITED, THE NUMBER AND AGE OF THE PARTICIPANTS, AND PROPOSED COMPENSATION: Participants will be recruited from courses taught within the College of Health and Human Performance. The principle investigator will asked the instructors permission before recruiting subjects. No student will be recruited from any class taught by the principal investigator. All subjects will be informed by the principal investigator as to what the study is investigating. A total of 24 voluntary subjects will be recruited. Subjects will range in age from 18-30 years. Subjects who have had knee surgery of any type, and subjects who have a history of knee pain other than anterior knee pain will be excluded from the study. There will be no direct compensation for any subject. 10. DESCRIBE THE INFORMED CONSENT PROCESS: To ensure the subjects voluntary, affirmative agreement to participate in the study informed consent will be obtained prior to any testing. A subject coding system will be used to protect each subjects confidentiality. Subjects will be assured that they may withdraw from the study at any time with no consequence. _____________________________ Principal Investigator _____________________________ __________ Principal Investigators Signature Date _____________________________ Supervisor _____________________________ __________ Supervisors Signature Date I approve this protocol for submission to the UFIRB: _____________________________ __________ Department Chairs Signature Date

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APPENDIX B INFORMED CONSENT Protocol Title: The effects of a patellofemoral knee brace on quadriceps muscle activation. Please read this consent document carefully before you decide to participate in this study. Purpose of the research study: The purpose of this research study is to determine the effects of a knee brace on thigh (quadriceps) muscle contraction using surface electromyography (a device that measures muscle activity). What you will be asked to do in the study: You will be asked to report for two testing times. The fist testing time will be to determine how much weight you can lift one time on a leg press and a leg extension exercise machine. Before doing this, you will first warm up by riding a stationary bicycle for three minutes. You will then perform five repetitions on the leg press machine with a very lightweight. The weight will continuously be increased and you will be asked to lift it one time. This will continue until we reach a weight you are unable to lift. After a five-minute rest you will be asked to repeat the same procedure on the leg extension machine. For the leg extension, you will only use the non-dominant leg (the one you not normally kick a ball with). You will be asked to return for the second session at least 48 hours later. At that time, your non-dominant leg will be prepped and five adhesive electrodes will be placed on the skin of your thigh muscles. If necessary a small area of skin will be shaved to allow for electrode placement and the skin will be cleaned with alcohol. These electrodes allow us to measure the muscle activity (how much it contracts) when you exercise. They only collect or read the electrical activity of the muscle, thus they do not transmit an electrical current into your body. You will be asked to lift the maximum weight obtained from the first session one time for each exercise. After that, you will be asked to lift a portion (85%) of the weight from the first day three times each, doing each exercise two times. One of the times you do the exercises you will be asked to wear the knee brace, the order is determined by chance. Your quadriceps muscle function will be recorded during each of the exercises. Once you are done with the second day of testing you have completed the study. If you have had knee surgery of any type or if you have a history of knee pain other than anterior knee pain you will not be included in the study. Time required: First testing session: 20 minutes Second testing session: 1 hour and 30 minutes 46

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47 Risks and Benefits: There are no direct benefits from your participation in this study. You may have some mild leg muscle soreness 24-48 hours following the study. As with any type of exercise, there is a slight risk of musculoskeletal injury such as a sprain or a muscle pull. A certified athletic trainer will be present to evaluate and treat any such injuries should they occur. Compensation: There is no compensation for your participation in this study. Confidentiality: Your identity will be kept confidential to the extent provided by law. Your information will be assigned a code number. The list connecting your name to this number will be kept in a locked file in my faculty supervisor's office. When the study is completed and the data have been analyzed, the list will be destroyed. Your name will not be used in any report. Voluntary Participation: Your participation in this study is completely voluntary. There is no penalty for not participating. Right to withdraw from the study: You have the right to withdraw from the study at anytime without consequence. Whom to contact if you have questions about the study: Carol Haskin, Graduate student, Department of Exercise and Sport Sciences (352) 235-0101 Dr. Michael Power, Ph.D., Assistant Professor, Department of Exercise and Sports Sciences (352) 392-0584 x1332 Whom to contact about your rights as a research participant in the study: UFIRB Office, Box 112250, University of Florida, Gainesville, FL 32611-2250; Phone number: 392-0433. Agreement: I have read the procedure described above. I voluntarily agree to participate in the procedure and I have received a copy of this description. Participant: ________________________________________ Date:_________________ Principal Investigator:__________________________________Date:_______________

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APPENDIX C DATA SHEET DATE_____________ ID # ____________ Leg tested R / L Size of Brace S / M / L / XL Gender M / F Age _____________ Height ___________ Weight ___________ 1-RM Knee Extension _______________ 75% KE ____________ 1-RM Leg Press ____________________ 75% LP _____________ Order of Conditions: 48

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APPENDIX D ANOVA TABLES Table E-1. ANOVA test results for VM. Source Sum of Squares df Mean Square F Significance Exercise .152 1 .152 .836 .371 Error 4.014 22 .182 Braced .342 1 .342 5.082 .034 Error 1.482 22 .0674 Phase of Ex 5.137 3 1.712 67.075 .000 Error 1.685 66 .0255 Ex*Brace .164 1 .164 3.417 .078 Error 1.058 22 .0481 Ex*Phase 4.057 3 1.352 59.67 .000 Error 1.496 66 .0227 Brace*Phase .107 3 .0356 4.917 .004 Error .477 66 .0723 Ex*Brac*Ph .0239 3 .0798 .772 .514 Error .682 66 .0103 Table E-2. ANOVA test results for VL. Source Sum of Squares df Mean Square F Significance Exercies 1.632 1 1.632 9.756 .005 Error 3.679 22 .167 Braced .0438 1 .0438 1.128 .300 Error .855 22 .0389 Phase of Ex 2.474 3 .825 43.778 .000 Error 1.243 66 .0188 Ex*Brace .0643 1 .0643 .024 .879 Error .593 22 .0269 Ex*Phase 4.505 3 1.502 75.24 .000 Error 1.317 66 .0199 Brace*Phase .0182 3 .0036 .750 .526 Error .317 66 .0048 Ex*Brac*Ph .0057 3 .0019 .238 .869 Error .524 66 .0079 49

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53 37. Morrish GM Woledge RC. A comparison of the activation of muscles moving the patella in normal subjects and in patients with chronic patellofemoral problems. Scandinavian Journal of Rehabilitation Medicine. 1997;29(1):43-8. 38. Muhle C, Brinkmann B, Skaf A, Heller M, Resnick D. Effect of a patellar realignment brace on patients with patellar subluxation and dislocation. The American Journal of Sports Medicine. 1999;27(3):350-353. 39. Natri A, Kannus P, Jarvinen M. Which factors predict the long-term outcome in chronic patellofemoral pain syndrome? A 7-yr prospective follow-up study. Medicine & Science in Sports & Exercise. 1998;30(11):1572-1577. 40. Ng GYF, Cheng JMF. The effects of patellar taping on pain and neuromuscular performance in subjects with patellofemoral pain syndrome. Clinical Rehabilitation. 2002;16:821-827. 41. Osternig LR, Robertson RN. Effects of prophylactic knee bracing on lower extremity joint position and muscle activation during running. The American Journal of Sports Medicine. 1993;21(5):733-737. 42. Podesta L, Sherman M. Knee bracing. Orthopedic Clinics of North America. 1988;19(4):737-745. 43. Powers CM. Rehabilitation of patelofemoral joint disorders: a critical review. Journal of Orthopaedic Sports Physical Therapy. 1998;28(5):345-354. 44. Powers CM, Landel R, Perry J, Rothstein J, Fitzgerald K, Karst G, Malone T, Wilk K. Timing and intensity of vastus muscle activity during functionsl activities in subjects with and without patellofemoral pain. Physical Therapy. 1996;76:946-955. 45. Powers CM, Shellock FG, Beering TV, Garrido DE, Goldbach RM, Molnar T. Effect of bracing on patellar kinematics in patients with patellofemoral joint pain. Medicine and Science in Sports and Exercise. 1999;31(12):1714-1730. 46. Rainoldi A, Bullock-Saxton JE, Cavarretta F, Hogan N. Repeatability of maximal voluntary force and of surface EMG variables during voluntary isometric contraction of quadriceps muscles in healthy subjects. Journal of Electromyography and Kinesiology. 2001;11:425-438. 47. Reid DC. The myth, mystic and frustration of anterior knee pain. Clinical Journal of Sports Medicine. 1993;3:139-143. 48. Rowlands BW, Brantingham JW. The efficacy of patella mobilization in patients suffering from patellofemoral pain syndrome. Journal of Orthopaedic Rheumatology. 1999;7(4):142-149

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54 49. Shellock FG, Mink JH, Deutsch AL, Molnar T. Effect of a newly designed patellar realignment brace on patellofemoral relationships. Medicine and Science in Sports and Exercise. 1995;27(4):469-472. 50. Shelton GL, Thigpen LK. Rehabilitation of patellofemoral dysfunction: A review of the literature. Journal of Orthopaedic Sports Physical Therapy. 1991;14(6):243-249. 51. Smith AD, Stroud L, McQueen C. Flexibility and anterior knee pain in adolescent elite figure skaters. Journal of Pediatric Orthopaedics. 1991;11:77-82. 52. Souza DR, Gross MT. Comparison of vastus medialis obliquus: vastus lateralis muscle integrated electromyographic ratios between healthy subjects and patients with patellofemoral pain. Physical Therapy. 1991;71:310-20. 53. Styf JR, Lundin O. Gershuni DH. Effects of a functional knee brace on leg muscle function. The American Journal of Sports Medicine. 1994;22(6):830-833. 54. Teitz CC, Hermanson BK, Kronmal RA, Diehr PH. Evaluation of the use of braces to prevent injury to the knee in collegiate football players. The Journal of Bone and Joint Surgery. 1987;69-A(1):2-9. 55. Thomee R, Augustsson J, Karlsson J. Patellofemoral pain syndrome: a review of current issues. Sports Medicine. 1999;28(4):245-262. 56. Timm KE. Randomized controlled trial of protonicson patellar pain, position, and function. Medicine & Science in Sports & Exercise. 1998;30(5):665-667. 57. Tortora GJ. Principles of Human Anatomy. Seventh edition. New York, Biological Sciences Textbooks. 1995. 58. Voight ML, Wieder DL. Comparative reflex response time of vatus medialis obliquus and vatus lateralis in normal subjects and subjects with extensor mechanism dysfunction. American Journal of Sports Medicine. 1991;19:131-7 59. Wilk KE, Davies GJ, Mangine RE, Malone TR. Patellofemoral disorders: A classification system and clinical guidelines for nonoperative rehabilitation. Journal of Orthopeadic and Sports Physical Therapy. 1998;28(5):307-322. 60. Witvrouw E, Lysens R, Bellemans J, Cambier D, Vanderstraeten G. Intrinsic risk factors for the development of anterior knee pain in an athletic population. The American Journal of Sports Medicine. 2000;28(4):480-489 61. Witvrouw E, Lysens R, Bellemans J, Peers K, Vanderstraeten G. Open versus closed kinetic chain exercises for patellofemoral pain: A prospective, randomized study. The American Journal of Sports Medicine. 2000;28(5):687-694

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55 62. Worrell T, Ingersoll CD, Bockrath-Pugliese K, Minis P. Effect of patellar taping and bracing on patellar position as determined by MRI in patients with patellofemoral pain. Journal of Athletic Training. 1998;33:16-20.

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BIOGRAPHICAL SKETCH I was born on August 2, 1979, in Charlotte, North Carolina to Edward and Julia Haskin. I grew up the younger sister of Eric Franklin on Markwell Drive in Matthews, North Carolina. This is the place where my parents continue to live and I still call home. I attended Matthews Elementary School and during this time I developed a love of sports by becoming active in tee-ball, coach pitch, and softball, and I also played the piano. I attended Randolph Junior High School from seventh to ninth grade. I began involvement with track in seventh grade and continued my love of softball, and piano. Providence Senior High School is where I spent my tenth through twelfth grade years. I became very active in cross-country, indoor track, outdoor track, and softball during high school. My interest in sports medicine began during this time. After graduating high school in 1997, I continued my education at the University of North Carolina at Chapel Hill. I began to expand my interest in sports medicine during my sophomore year and was accepted into the Athletic Training Program as a junior. I worked as a student athletic trainer with various men and womens collegiate teams as well as at a local high school. I graduated from UNC-Chapel Hill in May of 2001 with a Bachelor of Arts degree in exercise and sports science. I began work on my masters degree in August of 2001 at the University of Florida. While at UF I worked as a graduate assistant at Hawthorne High School in the local Gainesville area. My quest for a masters thesis began during this time. 56


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Title: The Effect of a patellofemoral knee brace on quadriceps muscle activity
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Creator: Haskin, Madelon Carol ( Author, Primary )
Publication Date: 2003
Copyright Date: 2003

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Permanent Link: http://ufdc.ufl.edu/UFE0001178/00001

Material Information

Title: The Effect of a patellofemoral knee brace on quadriceps muscle activity
Physical Description: Mixed Material
Creator: Haskin, Madelon Carol ( Author, Primary )
Publication Date: 2003
Copyright Date: 2003

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THE EFFECT OF A PATELLOFEMORAL KNEE BRACE ON QUADRICEPS
MUSCLE ACTIVITY















By

MADELON CAROL HASKIN


A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE IN EXERCISE AND SPORTS SCIENCE

UNIVERSITY OF FLORIDA


2003

































Copyright 2003

by

Madelon Carol Haskin















ACKNOWLEDGMENTS

I would like to take this opportunity to thank the numerous people who are

responsible for making this project possible. Without the cooperation, guidance, and

support of everyone around me, its completion would not have been possible. I would

first like to thank Dr. Powers for his help as committee chair. He was an endless source

of information and new ideas that aided me in my successful completion of this thesis.

I would also like to thank the members of my supervising committee. Dr.

Horodyski provided support and guidance in getting this project off the ground and I

thank her for this. She was also a valuable source of information, and her knowledge of

this topic contributed to its conclusion. Dr. Siders was also an important source of

information to improve my project. His knowledge of statistics was a helpful addition to

the data analysis of this topic. I would like to thank both Dr. Horodyski and Dr. Siders

for their patience towards the end of the project.

My gratitude goes out to Matthew Morgan for his role as my doctoral mentor.

These past two years have taken their toll, and Matt's availability has made it possible to

complete my master's work. As a novice at research, I depended on him, time and again,

to guide me.

The long hours of data collection for this project could not have been completed

without the help of my colleagues and friends. I would like to thank Kyle Smink for his

patience in sharing the lab equipment, as well as Dennis Valdez for his assistance during









data collection. My gratitude also goes to the SW Rec Center for the availability of the

facilities during testing.

Without the voluntary participation of all the subjects, the project would not have

been possible. Therefore, I would like to thank all of the men and women who completed

the exercise protocols for this project.

I would also like to thank my cousins Amy, Kim, and Joi for being such good

listeners and problem solvers. Without their help I would not have made it through this

thesis. My uncle Joe and Aunt Dawn have also been a much needed support. Finally, I

thank my parents, Edward and Julia, and my brother, Eric, for the twenty-four years of

unconditional love and support. Without them, I would never have made it to this point.

Regardless of the obstacles I face, they give me the strength to pull through with their

ceaseless love and encouragement.
















TABLE OF CONTENTS
page

A C K N O W L E D G M E N T S ......... .................................................................................... iii

LIST OF TA BLE S ......... .... ........ .... .... ...... ..................... .. .... vii

LIST OF FIGURES ......... ...... ..................................... .. ................. viii

ABSTRACT .............. ......................................... ix

CHAPTER

1 IN TR OD U CTION ............................................... .. ......................... ..

State ent of the Problem ............................................................................. ........ 2
H ypotheses ................................................ 3
D definition of T erm s ....................................................... 3
A ssum options ........................................................... ..........................
L im itatio n s ................................................................................. 4
Significance of Study ......................................... .............. .............. .5

2 REVIEW OF LITERATURE ......................................................... .............. 6

Patellofem oral Pain Syndrom e ............................................................................. 6
A natom y ................................................................7
C contributing F actors of PFP S .......................................................................... ...... 8
M alalignm ent..................................... .......................... ............. .. 9
M u scular Im b balance ....................... .......................... .... ........ .......... .. .. ....
P atellar T racking .......................................... ................... .. ...... 10
Vastus Medialis Oblique .......................................................10
Treatm ent for Patellofem oral Pain........................................................... ..... ........ .11
O operative ................................. .......................... ............................... 11
N o n -o p e rativ e ................................................................................................ 12
Q uadriceps strengthening .......................... ........... .... .................. 13
Patellofemoral taping ........................................................15
Patellofem oral bracing ........................................ ........................... 17
Electrom yography ....................................................... ...... ...............21

3 M E T H O D S ......................................................... ................ 2 4

S u b je cts ......................................................................... 2 4


v









Instrum entation ........... ............ ...... .. .................. ... ............... 24
Electrom yography (EM G )............................ ............................ ............... 24
Patellofemoral Knee Brace ............................... ................................. 25
M easurem ents ................................................................................................. .......25
One Repetition Maximum (1-RM) ............................................... ...............25
M u scle A ctiv ity ............................................................................................. 2 5
Procedures .................. ............................... 26
D ata A nalysis................................................... 27

4 R E S U L T S .............................................................................2 8

Subject D em graphics .......................................................................................... 2 8
V astu s M edialis ................................................................2 8
V astu s L ateralis ................................................................3 0

5 D ISC U S SIO N ............................................................................... 32

V astu s M edialis ................................................................32
V astu s L ateralis ................................................................3 3
Patellofemoral Bracing .............. ......... .......... ........33
P atellofem oral T aping ............................................................36
Exercise Comparison ....................... ............ ... ............... 37
C lin ical Im p licatio n s.............................................................................................. 4 0
S u m m a ry .................. ....... ............. .. ...............................................4 1
Im plications for Future R esearch.....................................................42

APPENDIX

A UNIVERSITY OF FLORIDA INSTITUTIONAL REVIEW BOARD ................ 43

B IN FO R M ED C O N SEN T .................................................................................... 46

C DATA SHEET............................................ 48

D ANOVA TABLES ........................................... ................. ............49

L IST O F R E FE R E N C E S ............................................................................... 50

B IO G R A PH IC A L SK E T C H ....................................................................................... 56
















LIST OF TABLES


Table page

4.1 Subject dem graphics (m eans SD). ......... ................................... ............... 28

4.2 Normalized VM activity during OKC and CKC knee extension (Mean SD)........29

4.3 Normalized VM activity during braced and unbraced conditions (Mean SD) ......29

4.4 Normalized VL activity during OKC and CKC knee extension (Mean SD).........30

E-1 AN OVA test results for VM ............................... .. ................................... 49

E-2 AN OVA test results for VL. ............................................ ............................ 49















LIST OF FIGURES


Figure page

5-1 VM EMG activity during braced conditionsignificantly greater than the
U nbraced Condition (P < 0.05) ........................................... ......................... 34

5-2 Concentric 450 to 0 of knee flexion during CKC and OKC exercises significant
interaction (P < 0.05)........... ...... .... ................... .... ..... .. ... 38

5-3 Eccentric 450 to 900 of knee flexion during CKC and OKC exercises significant
in teractio n (P 0 .0 5 )...................................................................... ................ .. 3 9















Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science

THE EFFECTS OF A PATELLOFEMORAL KNEE BRACE ON QUADRICEPS
MUSCLE ACTIVITY

By

Madelon Carol Haskin

August 2003

Chair: MaryBeth Horodyski
Major Department: Exercise and Sport Sciences

Patellofemoral pain syndrome (PFPS) is one of the most common musculoskeletal

disorders seen in sports medicine clinics today. The basic etiology of this syndrome

remains unknown. The exact cause of PFPS has been thought to vary from patient to

patient; therefore, a thorough investigation of history for each patient is necessary. The

methods to treat PFPS vary greatly ranging from quadricep strengthening to

patellofemoral bracing. Research has been conducted on the effects of the patellofemoral

brace on patellar alignment, but little is known on the effect of the patellofemoral brace

on quadriceps muscle activity. Therefore, the purpose of the present study was to assess

the effect of a patellofemoral knee brace on quadriceps muscle activity.

Twenty-three health subjects who had no history of previous knee injury

participated in this study. Prior to testing, each subject's 1-maximum repetition (1-RM)

for CKC(leg press), and OKC exercises (knee extension), were recorded. At least 48

hours later the subjects returned for testing. Electromyographic (EMG) electrodes were









placed over the non-dominant leg's vastus medialis (VM) and vastus lateralis (VL)

muscles, as well as the patella. A three-minute warm-up on a stationary bike was

followed by 5 repetitions of both the knee extension and leg press exercises performed at

75% of the subject's 1-RM. The order of conditions was randomized prior to testing.

Muscle activity was recorded using surface EMG during the concentric and eccentric

phases of each exercise. The data were analyzed to identify interactions.

The analyses demonstrated no significant interactions between knee extension and

leg press exercises during the braced and unbraced conditions. However, there was a

significant main effect between the braced and unbraced conditions regardless of exercise

type and phase of exercise. The results revealed greater muscle activation during the

braced condition versus the unbraced condition suggesting that a patellofemoral brace

positively effects muscle activity. Further research is needed to assess the effects a

patellofemoral knee brace on quadricep muscle activity during OKC and CKC exercises

with patellofemoral pain subjects.














CHAPTER 1
INTRODUCTION

The knee is a very important joint in the body, being involved in locomotion and

stability of the lower extremity.10 The knee's involvement in locomotion causes it to be a

common site for injury. These injuries can be painful and often debilitating taking an

athlete out of competition. Patellofemoral pain syndrome (PFPS) is one of the most

common musculoskeletal disorders affecting young adults.3'4 PFPS is often

misdiagnosed as anterior knee pain, chondromalacia patella, patellar pain syndrome,

patellofemoral arthralgia, patellar pain, and patellarfemoral pain.55 The basic etiology of

this syndrome is still unknown, but numerous predisposing factors have been mentioned

in the literature.42'55

Many muscles work together to enable the knee joint to be functional. The main

muscle groups are the pes anserinus, hamstrings, and the quadriceps. The pes anserinus

muscle group consists of the gracillis, sartorius, and the semitendinosus (a hamstring

muscle). The hamstrings are composed of the semitendinosus, semimembranosus, and

biceps femoris. The quadriceps include the vastus medialis, vastus lateralis, vastus

intermedius, and rectus femoris.

The vastus medialis obliquus muscle (VMO) of the quadriceps muscle group has

been thought to be a major contributor to patellofemoral joint pain. The VMO pulls the

patella medially during knee extension and has been reported to fire later than the vastus

lateralis (VL) in people with patellofemoral joint pain.55 This firing pattern may effect

patellar tracking, causing the patella to track laterally because the VMO is not firing on









time. Exercises that focus on VMO activity are emphasized to normalize the VMO:VL

firing ratio to correct the patellar tracking pattern. Reducing the abnormality of this ratio

has been thought to decrease patellofemoral joint pain.55 Knee braces, specifically

patellar braces, have been thought to help with this process. The patellofemoral knee

brace places pressure on the lateral side of the patella to deter lateral movement.4'42'55

There has been much debate on what type of rehabilitation program should be

implemented for athletes with patellofemoral pain. Treatment techniques frequently used

include quadriceps exercises focusing on the VMO, patellar taping, electrical stimulation

to guide quadriceps exercises, nonsteroidal anti-inflammatory agents, and patellofemoral

knee braces.3'28,49,59 A consensus on which rehabilitation program works best has not

been reached.

Knee pain is a common complaint in sports medicine clinics, accounting for 23 to

31% of the injuries. Of that percentage patellofemoral joint pain is the most common.

The high volume of patellofemoral injuries makes it important to understand the many

different ways to treat them. Previous studies have addressed the efficacy of

patellofemoral knee braces for the prevention or treatment of anterior knee pain.3'4'42

Only one study had been found that investigated muscle activity, and muscle activity

changes, while wearing a knee brace.23 Therefore, it becomes important to expand upon

previous research to understand what is happening muscularly while wearing a knee

brace.

Statement of the Problem

The VMO is a major focus in the rehabilitation of patellofemoral pain;

strengthening the VMO and improving the firing sequence with the VL are primary

concerns.1,3,7 While an athlete is progressing through rehabilitation, it is common practice









to have them wear a knee brace to facilitate greater medial tracking. The knee brace has

been shown to improve medial tracking, but the ramifications of potential changes in

VMO activity while wearing the brace have not been thoroughly studied.42 It has been

theorized that the VMO may not be as active while wearing the knee brace.23 Since the

brace is pushing the patella medially during knee extension, the VMO does not have to

work to pull the patella medially. If this is true, the knee brace may interfere with VMO

training during functional rehabilitation. Therefore, the purpose of this study was to

collect data on VMO and VL activity using surface electromyography (EMG) during

exercises, with and without a patellofemoral knee brace.

Hypotheses

Five hypotheses were identified for this investigation.

* Vastus medialis (VM) and Vastus lateralis (VL) muscle activity will be reduced
while wearing a knee brace as compared to not wearing a knee brace.

* Open kinetic chain (OKC) exercises will have greater VM and VL muscle activity
as compared to closed kinetic chain (CKC) exercises when performed without a
knee brace.

* OKC exercises will have greater VM and VL muscle activity as compared to CKC
exercises when performed with a knee brace

* OKC exercises will have greater VM and VL muscle activity as compared to CKC
exercises during the first 450 of motion when performed without a knee brace.

* OKC exercises will have greater VM and VL muscle activity as compared to CKC
exercises during the first 450 of motion done with a knee brace.

Definition of Terms

Four definitions were identified for this investigation.

* Closed kinetic chain (CKC) a movement whereby the foot or hand is on the
ground or some other surface.2 For the purpose of this study, the CKC exercise
involves the use of the leg press machine.









* Malalignment lower extremity alignment factors associated with PFPS include
femoral neck anteversion, genu valgum, knee hyperextension, Q angle, tibia varum,
and excessive rearfoot pronation.55

* Open kinetic chain (OKC) a movement whereby the foot or hand is off the
ground.2 For the purpose of this study, OKC involves the use of the lower
extremity performing concentric and eccentric knee extensions on the knee
extension machine.

* Patellofemoral Pain Syndrome (PFPS) anterior knee pain that is often diffuse and
along the medial aspect of the patella. Later, patellar pain and retropatellar pain are
also seen.44

Assumptions

Five assumptions were identified for this investigation.

* It was assumed that the subjects accurately performed all testing procedures as
instructed by the tester.

* It was assumed that the subjects performed all the testing procedures/exercises to
the best of their ability.

* It was assumed that all subjects gave accurate and honest answers to the medical
history questionnaire.

* It was assumed that the surface EMG detected and displayed accurate quadriceps
activity during the exercises.

* It was assumed that the brace remained in the proper location on the subject
throughout testing.

Limitations

Three limitations were identified for this investigation.

* All of the subjects tested had healthy knees with no previous history of
patellofemoral pain. Therefore, the subjects did not normally wear a patellofemoral
knee brace.

* Subjects may not have performed to their best ability during testing procedures.

* The subjects being tested did not have prior experience with a knee brace;
therefore, they were not acclimatized to the feel of exercise while wearing a knee
brace. Accommodation of the knee brace was not possible due to the limitation of
available knee braces.









Significance of Study

All rehabilitation programs should incorporate a functional aspect where the

rehabilitation exercises specifically mimic their sport. It is important to ensure that the

necessary muscles are being targeted during these functional exercises thereby enhancing

the rehabilitation process. Athletes with patellofemoral pain often continue to participate

in their chosen sport while going through a rehabilitation program. In order for continued

participation, the athletes may wear a knee brace to help decrease the pain during the

activity. Only one study had been found that determined the changes of muscular activity

while wearing a knee brace during open chain activities,19 while no known studies we

found that investigated CKC exercises. Does the knee brace prolong the rehabilitation

process by not allowing the VMO to be functionally rehabilitated? It is important for

athletic trainers to know if the application of a knee brace decreases the firing of the

VMO. The results of this study may give athletic trainers and rehabilitation specialist the

answer they need to adjust patellofemoral rehabilitation programs accordingly.

Therefore, once adjusted, VMO exercises done without the knee brace will not be in

contradiction with functional exercises done with the knee brace.














CHAPTER 2
REVIEW OF LITERATURE

In the literature, there have been numerous studies conducted on the issue of

Patellofemoral pain syndrome (PFPS). This topic is widely debated and there are many

different views on the causative factors of PFPS. No consensus exists on a generic PFPS

rehabilitation program. An overview of PFPS as well as a brief review of anatomy is

needed for the purposes of this study. A review of the current literature concerning PFPS

will reveal a need for more research in the area of rehabilitation.

Patellofemoral Pain Syndrome

Patellofemoral pain is the most frequent musculoskeletal disorder involving the

knee seen in sports medicine clinics.3'44 Many studies have verified the prevalence of

patellofemoral pain as the most common clinical condition presented to clinicians who

treat musculoskeletal conditions.59 Patellofemoral pain was demonstrated by Deveraux

and Lachmann12 to be the diagnoses of 25% of all knees evaluated in a sports injury

clinic over a five year period. According to McConnell,34 patellofemoral pain affects one

in four of the general population. In addition, the incidence of this disorder can also be

seen in a study conducted by Finestone et al.18 in a military setting. Throughout 14

weeks of basic training 84 out of 395 knees were diagnosed as having overuse

patellofemoral pain.18 This high incidence of patellofemoral pain seen in these studies

encourages more extensive research on the topic so that a better understanding and

consensus of treatment may be reached.









The symptoms of PFPS are many and often vary from person to person in severity.

The most common symptom in patients with PFPS is anterior knee pain. Pain is

generally diffuse and arising from the anterior aspect of the knee along the medial aspect

of the patella; however, lateral patella pain and retropatellar pain are also seen.44 This

anterior knee pain often arises during and after physical activity that increases

patellofemoral compressive forces. These activities include loading of the lower

extremity in walking up and down stairs, squatting, and prolonged sitting with knees

flexed.44'55 During an assessment of an athlete with patellofemoral pain the Patellar

Grind Test is often positive and palpation of the medial and lateral borders of the patella

cause pain.44 Some other symptoms that may be present include swelling, loss of motion,

and a sensation of giving way or instability of the knee joint.44

Anatomy

The knee joint is surrounded by many muscle complexes that work together

providing lower extremity stability and locomotion. The muscle complexes involved in

knee motion are the quadriceps, hamstrings, pes anserine, and

gastrocnemius/popliteus/plantaris. All of these muscles are involved in knee function and

most have some role on patellar tracking. Many bones are also involved in this joint and

they include the femur, patella, tibia and fibula.

The patella is classified as a sesamoid bone and it is the largest in the human body.

This sesamoid bone is located in the tendon of the quadriceps femoris muscle and is

triangular in shape. The patella articulates between the two femoral condyles in the

groove provided. The patella acts to increase the leverage of the tendon of the quadriceps

femoris muscle, maintaining the position of the tendon when the knee is flexed, and

protecting the knee joint. Patellar tracking within the groove is dependent upon the pull









of the quadriceps muscles and patellar tendon, the shape of the patella, and the depth of

the femoral condyles.2'57

The quadriceps muscles include vastus medialis (VM), vastus lateralis (VL), vastus

intermedius (VI), and rectus femoris (RF). The VM originates on the medial linea aspera

of the femur. The VM inserts into the tibial tuberosity via the quadriceps tendon, patella,

and patellar tendon. This muscle serves to extend the knee as well as function as a major

medial stabilizer for the patella.2 During knee extension the VM pulls the patella

medially due to its orientation relative to the patella. The VM is angled at

approximately 550 from the longitudinal axis of the femur aiding in medial patellar pull.44

The VL originates on the lateral linea aspera of the femur. It inserts into the tibial

tuberosity via the patella and patellar tendon. The VL also functions to extend the knee.

During knee movement and patellar tracking, the VL pulls laterally on the patella. The

VI originates on the anterior and lateral surfaces of the body of the femur. This muscle

also inserts on the tibial tuberosity via the patella and patellar tendon. The main function

of this muscle is knee extension pulling the patella proximally and laterally.2'57

The RF muscle is the only two-jointed quadriceps muscle. It originates on the

anterior inferior iliac spine, and attaches on the tibial tuberosity via the patella tendon.

This muscle functions as a hip flexor as well as a knee extensor. During patellar tracking

the RF muscle pulls the patella proximally and laterally.2'57

Contributing Factors of PFPS

The source of patellofemoral pain has been in debate and cannot be sufficiently

pinpointed. Authors suggest several possibilities as to the origin of PFPS described in

detail in the following paragraphs.









Several etiologies are mentioned by Brody and Thein7 in their review of

nonoperative treatments for patellofemoral pain. Intrinsic and extrinsic factors include

quadriceps insufficiency, hamstrings and iliotibial band inflexibility, lateral retinacular

tightness, femoral anteversion, a wide pelvis, excessive pronation, knee ligament injury,

acute trauma, instability, immobilization, and overuse.7'14'39 In a review of current PFPS

issues Thomee et al.55 discusses three major contributing factors of PFPS. These factors

include lower extremity and/or patellar malalignment, muscular imbalance, and

overactivity. Another factor contributing to PFPS involves abnormal patellar tracking

which may be caused by decreased VMO strength compared to the VL, or the firing rate

of the VL before the VMO.

Malalignment

Lower extremity malalignment factors include femoral neck anteversion, genu

valgum, knee hyperextension, quadriceps angle (Q-angle), tibia varum, and excessive

rearfoot pronation.55 These malalignment factors are seen in people with patellofemoral

pain, however these factors may also be seen in 60 to 80% of the normal population.

This questions the use of the term malalignment.47 Patellar malalignment refers to the

configuration of the trochlea and the inter-relationship between the patella and femoral

surfaces.55

Muscular Imbalance

Muscular imbalances associated with flexibility have been discussed as important

factors contributing to knee pain. This is usually referred to as quadriceps or hamstring

muscle tightness.55 This has also been demonstrated in decreased knee extensor strength

in people with PFPS, but it is undetermined whether this decreased strength causes or is a

result of PFPS.55 The muscular imbalance associated with firing sequence between the









VMO and the VL has also been discussed. The VMO has been shown to have a slower

reflex response time than the VL as measured by EMG.5 This type of imbalance may

lead to patellar tracking problems.

Patellar Tracking

A commonly accepted cause of patellofemoral pain is related to abnormal patellar

tracking within the trochlear groove which increases patellofemoral joint stress.44'25

Insall et al.,23 using radiographic examination, stated that patellar tracking abnormalities

were the major cause of patellar pain. This abnormal patellar tracking and increased joint

stress is believed to increase shearing and compression associated with articular cartilage

wear and subsequent degeneration.4 The articular cartilage itself has been dismissed as a

source of symptoms. It has been proposed that the subadjacent endplate is exposed to

pressure variations that would normally be absorbed by healthy cartilage, and this

pressure then stimulates pain receptors in the subchondral bone.20 This tracking problem

is believed to be caused by a muscular imbalance of the dynamic stabilizers of the patella.

This imbalance leads to excessive lateral forces in relation to the medially directed forces

acting on the patella.25 This patellar tracking problem has often been conservatively

treated by strengthening the dynamic stabilizers of the patella.22 These dynamic

stabilizers include pes anserinus and semimembranosus muscles, biceps femoris, VM,

VL, VI, and RF. The VMO has been implicated as being the primary medial stabilizer of

the patella.44

Vastus Medialis Oblique

The VMO has been identified as the distal fibers of the VM. Lieb and Perry30

stated that these distal fibers are angled approximately 550 from the longitudinal axis of

the femur. This increased angle gives the VMO a mechanical advantage allowing the









muscle to be proficient in preventing lateral patellar subluxation Consequently, the

VMO has been thought to counterbalance the lateral pull of the larger VL to ensure

patellar stability within the trochlear groove.30 The VMO is very important in this role,

and according to some studies investigators have found differences in VMO and VL

activity.52 These differences suggest that the lateral pull of the VL is not adequately

counteracted by the medial pull of the VMO. This greater lateral pull results in lateral

tracking and malalignment of the patella causing patellofemoral pain.43

VMO-VL firing rate differences have been thought to be another contributing

factor to PFPS. In studies were the VMO had been thought to be weaker than the VL,

authors suggest that the timing of the muscle contractions may also differ. The VL has

been believed to contract before the VMO in concentric and eccentric quadriceps activity

instead of simultaneously.43 This hypothesis has been supported by Voight and Wieder58,

who found that activation of the VMO in subjects with patellofemoral pain was delayed

as compared to the VL during a patellar tendon tap. Morrish and Woledge37 also reported

a shorter reflex response time of the VL compared to the VMO in patients with

patellofemoral pain. In contrast, normal individuals had significantly earlier VMO firing

versus the VL in the same study. In contrast, a study conducted by Powers et al.43 found

no timing or intensity differences between the VM and VL in patients with

patellofemoral pain.

Treatment for Patellofemoral Pain

Operative

Operative treatment for patellofemoral pain should always be a last resort, and only

if nonoperative conservative treatments have been unsuccessful. These treatment

methods are often directed at treating malalignment, extensor mechanism abnormalities,









or injured cartilage.5 Some of these operative treatments include lateral retinacular

release, proximal realignment procedures, elevation of the tibial tubercle, anteromedial

tibial tubercle transfer and elevation, articular cartilage procedures, and patellectomey.55

Non-operative

Non-operative treatment of patellofemoral pain is always preferable to operative

treatment. Every non-operative protocol should be exhausted before surgery is

considered. A successful non-operative or conservative treatment first requires a

thorough analysis of predisposing anatomical, physiological and lifestyle factors. Once

these have been established the causative factor of the pain may be identified and

corrected through a rehabilitation program. Conservative interventions include patient

education, mobilization techniques, modalities, medications, acupuncture, quadriceps

strengthening, taping, and bracing.'7 These have also been used in combination to create

a well rounded rehabilitation program.3'5'7

Patient education is very important with any injury and especially with

patellofemoral pain. The patient must be informed on the contributing factors and the

treatments available, therefore enabling them to modify and minimize possible causes of

their pain. Patient education is also important for recurrent patellofemoral pain, so the

patient may avoid exacerbating symptoms.7 Self-management becomes an important role

in the long-term care of knee injuries. Patient education should come first in the

management of patellofemoral pain followed by the chosen rehabilitation protocol.

Mobilization techniques such as patellar manipulation and muscle stretching have

been investigated as non-operative treatments of patellofemoral pain. Patellar

mobilizations can be applied when soft tissue shortening produces an imbalance such as a

lateral glide, tilt, or rotation of the patella. Rowlands et al.48 compared a group of









patients who received a patellar mobilization procedure with a group that received

detuned ultrasound. The patellar mobilization involved a manual sustained glide

followed by high-velocity low-amplitude manipulation. The patellar mobilization group

demonstrated significantly lower levels of pain than the control group at a 1-month

follow-up, but no difference was found in functional outcome between groups.48

Muscle stretching techniques involve the lateral structures of the knee such as the

iliotibial band, lateral retinacular tissues, and other surrounding muscular complexes such

as the quadriceps, hamstrings, and gastrocnemius. Doucette and Goble13 studied patients

with lateral patellar compression, and found that after an 8-week rehabilitation program

the patients that were pain free had an improved Ober's test and an improved congruence

angle averaging 6.60. A study conducted by Smith et al.51 found a correlation between

patellofemoral pain and poor hamstring and quadriceps flexibility. Tightness in the

gastrocnemius muscle can contribute to patellofemoral pain by increasing dynamic

pronation, which in turn increases patellofemoral joint reaction forces.7,15,27,50

The goal of modalities in the treatment of patellofemoral pain is to decrease pain.

This is primarily achieved through the use of ice, however ultrasound, phonophoresis,

and iontophoresis have also been used.1'7 Modalities such as electrical stimulation have

been used to facilitate quadriceps muscle activity. Bohannon6 used VMO electrical

stimulation to prevent patellar subluxation during a rehabilitation protocol. Electrical

stimulation is helpful in muscle reeducation for individuals with acute pain, edema, or

significant weakness who are unable to activate their quadriceps.7

Quadriceps strengthening

Quadriceps strengthening is an important part of patellofemoral pain rehabilitation.

A rehabilitation program often consists of a combination of quadriceps strengthening and









another chosen non-operative treatment.7 The mechanism by which strengthening

decreases patellofemoral pain symptoms and functional ability has not been established.

The wide spread use of this method indicates its importance in the over all PFPS

rehabilitation process.

Natri et al.39 investigated factors that may predict long-term outcome in chronic

PFPS. Forty-nine subjects with unilateral PFPS were enrolled in the study and underwent

a 6-week conservative treatment protocol. The protocol consisted of rest, nonsteroidal

anti-inflammatory medication, and intensive quadriceps strengthening exercises. A

follow-up evaluation was performed at 6 months and 7 years post the 6-week protocol.

The results of the study indicated that restoration of quadriceps strength and function to

the affected extremity was important for long-term patient recovery.

Witvrouw et al.61 investigated open kinetic chain (OKC) versus closed kinetic

chain (CKC) exercises for patellofemoral pain. The subjects were divided into two

groups and they either performed OKC or CKC exercise protocols. Each subject was

evaluated with a subjective outcome assessment, functional outcome assessment, muscle-

strength measurement, and muscle length measurement prior to 5 weeks into training, and

3 months after training. The CKC group had a few significantly better functional results

for some of the tested parameters compared to the OKC group. However, after the

protocols were completed both groups demonstrated a significant increase in overall

functionality, as measured by the Kujala scale, and a decrease in pain. Therefore, the

authors concluded that both OKC and CKC exercises lead to improved subjective and

clinical outcome scores in patients with anterior knee pain.61









Another study was conducted by Doucette and Goble13 to assess exercise on

patellar tracking. Twenty-eight subjects and 56 knees diagnosed with lateral patellar

compression syndrome were studied. The subjects participated in a five-stage

rehabilitation program designed to meet each subject's specific needs using VMO

exercises. These exercises included straight leg raises (SLR) with external rotation,

squats, seated leg press, single knee dips, and others. Doucette and Goble13 found that

patellar tracking was improved with VMO strengthening in lateral patellar compression

syndrome.

All of the above studies focused on quadriceps strengthening exercises to decrease

PFPS symptoms. Strengthening with a patellofemoral brace was not studied in any of

these studies. The exercises used to strengthen the quadriceps in a PFPS rehabilitation

protocol need to be investigated while wearing a patellofemoral knee brace.

Patellofemoral taping

Patellofemoral taping is another method employed by rehabilitation specialists to

treat PFPS. This technique was devised by McConnell and has been utilized to create a

passive correction of lateral patellar tracking, tilt, and rotation.28 Studies investigating its

ability to correct patellar alignment during quadriceps rehabilitation thereby decreasing

pain associated with PFPS have been conducted.34'16 Other investigations include EMG

activity of the quadriceps with and without patellar taping19'40 and patellofemoral taping

used in combination with other treatments such as exercise and modalities mentioned

above.

Worrell et al.62 investigated the effect of patellar taping on patellar position as

determined by magnetic resonance imaging (MRI) in patients with patellofemoral pain.

Static MRI was used with the knee at eight different angles of knee flexion to determine









the placement of the patella in the trochlear groove. Patellar placement was determined

by digitization of patellofemoral congruence angle, lateral patellar displacement, and

lateral patellar angle. The authors concluded that patellar taping influenced patellar

position, produced less lateral patellofemoral congruence angle, and a more medial lateral

patellar displacement, at 100 of knee flexion during the static MRI.

Another study conducted by Kowall et al.28 also studied patellar taping in the

treatment of patellofemoral pain. This study incorporated a control group utilizing a

physical therapy program and a second group that underwent a physical therapy program

combined with patellar taping. The activity of the VM and VL muscles were assessed

during a CKC step-up and step-down exercise using surface electromyography (EMG)

electrodes. Both groups experienced a statistically significant decrease in the frequency

of pain, but no significant difference between the groups in their improvement as

measured by a visual analog pain scale. The EMG activity of the symptomatic knees

increased significantly from the beginning to the end of therapy for both groups, which

was not seen in the asymptomatic knees. The increase in EMG activity was not

significantly different between the two testing groups.28

Ernst et al.16 investigated knee kinetics with and without patellar tape in patients

with PFPS. This study examined the effect ofMcConnell patellar taping on a single-leg

vertical jump and lateral step-up. Maximal knee extensor moment, knee power, and

vertical jump height were measured using a force platform and motion analysis system.

The results indicated greater knee extensor moment and power with patellar taping than

without.16









The effect of patellar taping on pain and neuromuscular performance was studied in

subjects with patellofemoral pain by Ng and Cheng40. The study was a pre-test post-test

treatment design with the order of treatment randomized. Fifteen subjects performed a

single leg stance with the stance leg in 300 of knee flexion and wearing a weight belt

equivalent to 20% of their body weight, with and without the patellar tape. The results of

the study indicated that patellar taping significantly decreased patellofemoral pain and

VMO to VL EMG ratio. The VMO was found to be less active with the patellar tape and

the researchers advised caution when taping and rehabilitation for PFPS are used

together.40 This study indicated that further research is needed on this topic, possibly

including patellofemoral bracing and EMG activity.These same results may occur with

application of a patellofemoral brace which may undermine rehabilitation protocols,

therefore further research is warranted.

A similar study was conducted by Gilleard et al.19 on the effect of patellar taping on

the onset of VMO and VL muscle activity in persons with patellofemoral pain. Fourteen

female subjects with patellofemoral pain walked up and down stairs with and without

patellar taping. The results indicated that taping of the patellofemoral joint changed the

timing of the VMO and VL activity during step-up and step-downs in patients with

patellofemoral pain. The onset of VMO activity in particular occurred earlier with

patellar taping during both tasks.19 These conclusions are in contrast to the above study

indicating that further research in the area of EMG activity and patellar realignment

devices are needed.

Patellofemoral bracing

Patellar braces are designed to assist in correct tracking of the patella in the

trochlear groove, to decrease pain, and prevent patellar subluxation or dislocation.42









These patellar braces are normally constructed of neoprene material with or without a

patellar relief hole in the sleeve over the patella. Felt, rubber, or gel inserts may be

placed in positions above, below, medial, or lateral to the patella to limit and control

patellar tracking as the knee extends.42 These braces may also include medial and lateral

stays to provide stability to the brace and to prevent wrinkling of the elastic material.42

The use of patellofemoral bracing as a treatment technique and its effect on

quadriceps muscle activity is what this study is focusing on. Many studies have been

conducted advocating the use of a patellofemoral brace in either prevention or treatment

of patellofemoral pain.4'31'49 A few studies indicated no significant relationship between

bracing and patellar kinematics. Only one study had been found that investigated EMG

activity of the VMO and VL with and without the use of a patellofemoral knee brace.21

These studies will be discussed to indicate the further need for more research.

A study conducted by Worrell et al.62 investigated the effect of patellar taping and

bracing (Palumbo Brace, DynOrthotics LP, Vienna, VA) on patellar position as

determined by MRI in patients with patellofemoral pain.62 During the study, static MRI

images were taken at 8 different angles of knee flexion. It was concluded that patellar

bracing and taping influenced patellar position at 100 of knee flexion during a static MRI

condition. The researchers also agree that more investigation is needed to determine

etiological factors and long-term outcomes of conservative and surgical treatment.62

Shellock et al.49 were involved with a case study to determine the effect of applying

a newly developed patellar realignment brace to a patient with lateral subluxation of the

patella. The brace had a viscoelastic silicone insert with a guide designed to counteract

patellar subluxation. MRI information taken during active movement indicated that the









brace corrected the lateral displacement of the patella. The patient involved in the study

also underwent physical rehabilitation and had no painful symptoms 4 months later.49

This was a case study involving only one subject; therefore, more research is needed with

additional subject participation to determine the effect of the patellar realignment brace.

Another research team, BenGal et al.4 investigated the role of the knee brace in

prevention of anterior knee pain. The knee brace incorporated a silicon patellar support

ring and was worn by 27 subjects (21 men, 6 women), who had no previous history of

anterior knee pain, while performing increasingly intensive exertion exercises. As the

exercise intensity increased, anterior knee pain syndrome appeared more frequently.

Male athletes wearing the braces before the exercise sessions had significantly less

incidence of PFPS than those that did not wear the brace. The researchers concluded use

of the knee brace may be an effective way to prevent anterior knee pain in people

performing intensive physical activity.4 More intensive investigation needs to be

completed regarding this subject, feasibility prevents everyone participating in intensive

physical exercise from wearing a knee brace. A look at what the knee brace is

accomplishing while being worn needs to be investigated.

Another investigation was done on the patellar brace to assess its effect on

performance in a knee extension strength test in patients with patellar pain.31 Lyshom et

al.31 used a Cybex-II to test strength performance with and without the brace in 24

patients with patellofemoral arthralgia. Twenty-one patients improved their performance

in the strength test with the brace than without the brace. Fourteen patients performed at

least 95% of their control leg strength while wearing the brace. The researchers

concluded that the results support the use of this brace in conservative management of









patients with patellofemoral arthralgias.31 The researchers in this study also advocate the

use of a brace as a supplement in a quadriceps rehabilitation program to improve the

effect of the training.31 The activity of the quadriceps needs to be examined while

wearing the patellar brace to determine if this supplementation during quadriceps

rehabilitation is appropriate.

Contrary to the above studies, Muhle et al.38 found no stabilizing effect of the

tested brace in patients with patellar subluxation or dislocation during active joint motion.

Muhle et al.38 examined 21 patients with clinical evidence of patellar subluxation or

dislocation with kinematic MRI with and without a patellar realignment brace. The

researchers found no statistically significant differences in the patellofemoral

relationships before or after wearing the patellar brace.

The study conducted by Powers et al.45 indicated similar results concerning the

effect of bracing on patellar kinematics in patients with patellofemoral joint pain.

Kinematic MRI of the patellofemoral joint was taken through the ranges of 45 to 00 of

knee flexion with and without a patellofemoral joint brace. The results indicated no

statistically significant difference between the braced and unbraced trials.

One study was done concerning patellar bracing and its effect on quadriceps EMG

activity. This study was conducted by Gulling et al.21 on 16 athletically active

individuals who were all concurrently participating in physical therapy. All subjects

demonstrated symptoms indicative of PFPS but had no history of knee surgery or

traumatic knee ligamentous injury. Each subject was then tested on an isokinetic

dynamometer (Kin-Com) with and without the patellofemoral brace (U1004-patellar

stabilizer). Surface EMG activity was recorded from the VMO and VL during three









maximal concentric/eccentric quadriceps contractions at an angular velocity of

1800/second. The EMG data indicated that the application of the patellar brace produced

significantly smaller IEMG (integrated EMG) signals than the non-braced condition in

both muscles and both contractions.21 The IEMG data were also significantly greater for

the VMO than the VL in both conditions, and during the concentric muscle contraction

compared to the eccentric muscle contraction.

The results demonstrate that patellar bracing may lower neuromuscular activation

of the quadriceps muscles during isokinetic knee extension. The researchers suggested

this decrease of IEMG activity was a contribution in the reduction of symptoms of PFPS.

By reducing stronger muscle contractions lateral patellar tracking may incidentally be

reduced also.21 This study was conducted with only an OKC exercise. Similar

investigations conducted with CKC are needed. Additionally, a study on a non-injured

population would give researchers a better idea of the patellar brace's effect on

quadriceps activity. Further investigation is warranted to support or refute the findings of

this study.

Electromyography

Surface EMG has been used in research to detect muscle activation. More

specifically surface EMG has been used in studies when the activity of the quadriceps

muscles was collected.19,24,29,33,40 There are many considerations that must be addressed

when surface EMG is utilized.

A differential electrode configuration should be used with surface EMG. This

configuration relates to the detection surface of the EMG electrode. This detection

surface should consist of two parallel bars, both 1.0 cm long, 1-2mm wide, and 1.0 cm

apart. A bandwidth of 20-500 Hz should be used with a roll-off of at least 12dB/octave,









and a common mode rejection ratio of >80dB. The noise should be <2uV rms (20-400

Hz) and an input impedance > 100 meg ohms.11

The two electrodes should be placed on the midline of the muscle belly to receive

the best signal. The electrodes on the midline of the muscle belly need to be between the

myotendinous junction and the nearest innervation zone. The detection surfaces should

be oriented perpendicular to the length of the muscle fibers."

Gulling et al.21 conducted a study on the effects of patellar bracing on quadriceps

EMG activity during isokinetic exercise. The EMG electrodes were placed in the centers

of the VMO and VL muscle bellies along the longitudinal axis of the muscle fibers and

the centers of the electrodes were placed 3.0 cm apart. The two ground electrodes were

placed over the medial and lateral malleoli. Raw EMG signals were collected at a

sampling frequency of 1000 Hz, pre-amplified at a 1,000,000:1 gain, and processed

through an analog to digital (AD) conversion. This rectified EMG activity was then

integrated and stored on an IBM microprocessor and analyzed over the 10-35 degree arc

of motion.21 This type of EMG set-up is similar to the process that will be utilized in the

current study.

Ng and Cheng40 used a similar set up in a study investigating the effects of patellar

taping on pain and neuromuscular performance in subjects with PFPS. Two pairs of

Ag/Ag Cl surface electrodes with a diameter of 1 cm were used to record the EMG

muscle activity of the VMO and VL. These electrodes were placed over the mid-point of

both muscles along the muscle fiber directions. Each electrode on the same muscle was

separated by 2.5 cm. The electrodes were attached to an input box and an amplifier that

performed linear enveloping between 15-1000 Hz and a differential amplification of









1000x. The common mode rejection ratio (CMRR) of the amplifier was 80dB. The

rectified full wave signal was input into an AD converter, which sampled at 2500 Hz and

the digitized signals were sent to a personal computer with Global Lab software for

analysis.4

Lam and Ng29 investigated the activation of the quadriceps muscle during

semisquatting with different hip and knee positions in patients with anterior knee pain.

This study did not apply patellofemoral tape or a brace during the exercises. Active

surface electrodes with a built-in gain of 1000x and a band pass filter of 20-450 Hz were

applied along the fiber direction of the muscles to detect muscle signals. Raw EMG

signals were input into a data acquisition unit that performed AD conversions at a

sampling frequency of 500 Hz. This digitized EMG data were then integrated over time

and output to a personal computer for display and storage.29

The above studies used similar EMG parameters to determine muscle activation.

These parameters varied depending on the type of software that was utilized for each

individual study. Many of these parameters seen in the above studies will be utilized in

the current study and will vary according to the software utilized.














CHAPTER 3
METHODS

The goal of this study was to gain information that would help in the development

of rehabilitation protocols for patellofemoral pain. These protocols may change to

benefit the athlete with a greater understanding of muscle function when performing

these exercises with and without the patellar stabilizing brace. To accomplish this we

utilized a within subject repeated measures design.

Subjects

Twenty-three healthy subjects from the University of Florida's student body were

recruited for this investigation. The subjects were between the ages of 18 and 30 years

and did not have a history of any lower extremity injury. The subjects were also

resistance trained and familiar with the knee extension and leg press exercise. Prior to

participating, each subject read and signed an informed consent agreement approved by

the university's Institutional Review Board.

Instrumentation

Electromyography (EMG)

A Myopac EMG system (Run Technologies, Laguna Hills, CA) was used to collect

the raw EMG signal. The unit specifications for the EMG included a frequency

bandwidth of 10-1000 Hz, CMRR of 110 dB, input resistance of 1 MQ, and a sampling

rate of 2000 Hz. Following sampling, EMG data underwent an AD conversion and was

stored on a PC-type computer using the DATAPAC 2000 (Run Technologies, Laguna

Hills, CA) analogue data acquisition, processing, and analysis system.









Patellofemoral Knee Brace

The Patella Stabilizer with Universal Buttress by Mieller was utilized for this

study. This knee brace is secured to the leg by two Velcro straps, one below and one

above the patella. Four different sizes (S, M, L, XL) were available for use by the

subjects depending on the manufactures specifications of each subject's knee and calf

girth.

Measurements

One Repetition Maximum (1-RM)

The 1-RM test followed light cycling on a stationary cycle for 3 minutes and a

warm-up set of 10 repetitions using low resistance (approximately 10% of body weight

for the knee extension and 50% of body weight for the leg press). The 1-RM test for the

knee extension exercise was assessed first, followed by the leg press. A five-minute

recovery period was taken between exercises. For both exercises the weight was

progressively increased (2.2kg for the knee extension and 4.4kg for the leg press) until

the subject could no longer complete the concentric phase of the lift unassisted. The

maximal weight the subject was able to lift concentrically unassisted was used as the 1-

RM

Muscle Activity

Quadriceps muscle activity of the dominant leg during open kinetic chain (OKC)

and closed kinetic chain (CKC) knee extension was determined from the amplitude of the

EMG signal. To begin this procedure, each subject's skin was shaved and cleaned with

isopropyl alcohol to reduce skin impedance. Immediately following, bipolar 1-cm

Ag/AgCl surface electrodes were placed parallel with the muscle fibers at a point midway

between the motor point and the musculotendinous junction of the vastus medialis (VM)









and vastus lateralis (VL) using an inter-electrode distance of 1.5-cm. The electrode

placements were confirmed with manual muscle testing and checked for cross-talk with

real time oscilloscope displays.

After placement was confirmed, the maximal EMG activity of both muscles were

measured and recorded during a 1-RM lift on the leg press and the leg extension machine.

After a brief rest period, muscle activity was recorded during the concentric and eccentric

phases of each exercise, which was done at 75% of the subject's 1-RM. The first 450 and

the second 450 of both the concentric and eccentric phases of each exercise were marked

on the EMG with a manual switch controlled by the researcher. This manual switch was

activated at the start of the concentric phase and released on the eccentric phase to

distinguish the different contractions from each other on the EMG signal. The acquired

raw signals were digitally processed using a symmetric root mean square (RMS)

algorithm, with a 10-msec time constant. All muscle activity recorded during testing was

expressed as a percentage of the normalization base (% 1-RM).

Procedures

Each subject reported to the Athletic Training/Sports Medicine Research

Laboratory on two separate occasions. During the first session, each subject was

assessed for his or her 1-RMon the leg extension and leg press exercises. When the 1-

RM testing was completed the session was over and the subject was free to leave.

The subjects returned for the second session after a period of at least 48-hrs

following the first session. During this session, each subject was assessed for quadriceps

activity while performing both the knee extension and leg press exercises. For each

exercise the resistance used was equivalent to 75% of the previously determined 1-RM.

The subjects were also assessed under two conditions during these exercises; braced and









unbraced. During the braced condition, each subject wore a patellar stabilizing brace on

the dominant leg. The brace was fitted according to the manufacturers specifications and

based on the circumference of the knee and calf. The order of the four conditions; OKC

braced, OKC unbraced, CKC braced, and CKC unbraced were randomly assigned and

counterbalanced. A five-minute recovery period separated each condition.

After the 1-RM was done on the second day for normalization of the EMG, the

knee extension and leg press exercises were performed. Five repetitions of each exercise

were performed and the measurement took place during both the concentric and eccentric

phases. A switch controlled by the researcher distinguished the concentric phase from

the eccentric phase. A metronome was used to control for the rate of movement, which

consisted of a three-second concentric and a three-second eccentric phase. When all four

conditions were completed the session was over and the subject was free to leave.

Data Analysis

SPSS 11.0 for Windows (SPSS, Inc., Chicago, IL) was used for statistical analysis.

Two repeated-measures ANOVAs with three within-subject factors were used to analyze

the data. The three factors were exercise (OKC, CKC), treatment(braced, unbraced),

phase of exercise (first and final 450 concentrically, first and final 450 eccentrically). An

ANOVA was completed for each muscle (VM, VL). Tukey's HSD Post hoc analyses

were used to locate the differences of interest if significant interactions resulted from the

ANOVAs. An alpha level of p < .05 was set apriori for all statistical analyses.














CHAPTER 4
RESULTS

The purpose of this study was to examine the effects of a patellofemoral knee brace

on quadriceps muscle activity during open kinetic chain (OKC) and closed kinetic chain

(CKC) knee extension exercises. Male and female college-age subjects were recruited

for this study. Each subject performed OKC and CKC chain exercises with and without a

brace in a randomly assigned order. Quadriceps electromyographic (EMG) activity was

recorded for each condition.

Subject Demographics

Twelve male and 11 female students from the University of Florida participated in

this study. All of the subjects were healthy and had no history of previous knee injury.

Subject demographic data are presented in Table 4.1.

Table 4.1 Subject demographics (means SD).
Subjects Age (y) Height (cm) Weight (kg)
N= 23 232.71 171.066.96 68.9112.17

Vastus Medialis

The ANOVA for vastus medialis (VM) EMG activity did not reveal a significant

interaction between the type of exercise, the braced condition, and the phase of exercise

[F(3,92)=0.772, p=0.514]. It also failed to reveal a significant interaction between the type

of exercise and the braced condition [F(1,92)=3.417, p=0.078]. However, a significant

interaction between the type of exercise and the phase of exercise [F(3,46)=59.67, p=0.000]









was revealed. The Tukey HSD post hoc analysis determined that differences of 4.44% or

greater were considered significant (Table 4.2).

Table 4.2. Normalized VM activity during OKC and CKC knee extension (Mean
Concentric Eccentric
Exercise 900 to 450 450 to 00 00 to 450 450 to 900
OKC 90.04.4% 78.84.4%* 60.53.6% 68.83.3%
CKC 84.04.8% 44.43.8% 59.83.8% 93.64.8% t
* Significantly greater than CKC during same phase of exercise (p<.05).
t Significantly greater than OKC during same phase of exercise (p<.05).

A statistically significant interaction was also observed between the braced condition and

the phase of exercise [F(3,46)=4.917, p=0.004]. The Tukey HSD post hoc analysis

determined that differences of 4.44% or greater were considered significant (Table 4.3).

Table 4.3. Normalized VM activity during braced and unbraced conditions (Mean
Concentric Eccentric
Exercise 900 to 450 450 to 00 00 to 450 450 to 900
Braced 91.45.0%* 62.04.1% 62.93.8% 85.93.9% *
Unbraced 82.63.2% 61.22.7% 57.42.6% 76.62.5%
* Significantly greater than unbraced during same phase of exercise (p<.05).

The ANOVA for the VM revealed no significant main effect for exercise type

[F(1,23)=.836, p=0.371], suggesting no difference in EMG activity between OKC and

CKC knee extension. However, significant main effects for braced condition

[F(1,23)=5.082, p=0.034] and phase of exercise [F(3,92)=67.075, p=0.000] were

observed. The normalized EMG activity when the knee brace was used (75.5 3.9%)

was significantly higher than when it was not used (69.4 2.3%). The Tukey HSD post

hoc analysis for the phase of exercise determined that differences of 3.4% or greater were

considered significant. Therefore, the normalized EMG activity when the VM was

contracting eccentrically from 450 to 900 of flexion (81.2 +3.0%) was significantly









greater than when it was contracting eccentrically from full extension to 450 of flexion

(60.1 +3.0%), and when it was contracting concentrically from 450 of flexion to full

extension (61.6 3.1%). However, the normalized EMG activity during the same phase

of exercise was significantly lower than when the VM was contracting concentrically

from 900 to 450 of flexion (87.0 3.8%).

Vastus Lateralis

The ANOVA for vastus lateralis (VL) EMG activity did not reveal a significant

interaction between the type of exercise, the braced condition, and the phase of exercise

[F(3,46)=0.750, p=0.526]. It also failed to reveal significant interactions between the type

of exercise and the braced condition [F(1,92)=.024, P=.879] and between the braced

condition and the phase of exercise [F(3,46)=0.750, p=0.526]. However, a significant

interaction between the type of exercise and the phase of exercise [F(3,46) 75.20, p=0.000]

was revealed. The Tukey HSD post hoc analysis determined that differences of 4.44% or

greater were considered significant (Table 4.4).

Table 4.4. Normalized VL activity during OKC and CKC knee extension (Mean SD)
Concentric Eccentric
Exercise 900 to 450 450 to 00 00 to 450 450 to 900
OKC 86.94.3% 86.74.2% 66.04.2% 66.34.2%
CKC 74.52.9% 40.72.9% 54.62.6% 82.83.3% t
* Significantly greater than CKC during same phase of exercise (p<.05).
t Significantly greater than OKC during same phase of exercise (p<.05).


The ANOVA for the VL revealed no significant main effect for the braced

condition [F(1,23)=1.128, P=0.300]. However, significant main effects for the type of

exercise [F(1,23)=.9.756, P=0.005] and the phase of exercise [F(3,92)=43.778, p=0.000] were

revealed. The normalized EMG activity of the VL was greater during OKC exercise









(76.5 3.7%) as compared to CKC exercise (63.2 2.5%). The Tukey HSD post hoc

analysis determined that differences of 3.40% or greater were considered significant. The

normalized EMG activity when the VL was contracting eccentrically from 450 to 900 of

flexion (74.6 2.8%) was significantly greater than when it was contracting eccentrically

from full extension to 450 of flexion (60.3 2.9%), and when it was contracting

concentrically from 450 of flexion to full extension (63.7 2.6%). Also, the normalized

EMG activity was significantly greater when the VL was contracting concentrically from

900 to 450 of flexion (80.7 2.3%) as compared to all other phases of the knee extension

exercises.














CHAPTER 5
DISCUSSION

The primary goal of this investigation was to determine if a patellofemoral knee

brace would alter quadriceps activity during open kinetic chain (OKC) and closed kinetic

chain (CKC) knee extension exercises. To accomplish this we examined 23 subjects

without a history of knee pain. Quadricep electromyographic (EMG) activity of the

vastus medialis (VM) and vastus lateralis (VL) were obtained from each subject while

they performed OKC and CKC exercises with and without a knee brace. Two ANOVAs

were utilized to analyze the data collected.

Vastus Medialis

We initially hypothesized that VM activity would be reduced when the subjects

wore the knee brace compared to when they did not. We further hypothesized that this

would occur regardless of the type of exercise (OKC versus CKC). However, this did not

occur, as VM activity during both the OKC and CKC exercises increased when the knee

brace was worn. Specifically, when the data from both exercises and each phase of

exercise were pooled together, the VM activity was actually greater during the braced

condition. When separated by phase of exercise, the braced conditions resulted in greater

activity both concentrically and eccentrically when the knee was in the more flexed

phase. Bracing had no effect on VM activity during the final 450 of knee extension.

VM activity was greatest when the muscle was contracting concentrically from 450

of flexion to full extension. This was not affected by the knee brace. When the type of

exercise was compared, VM activity during this phase was significantly greater in the









OKC compared to the CKC. However, when the VM was contracting eccentrically from

450 to 900 of flexion, the activity was greater in the CKC.

Vastus Lateralis

Like the VM, we initially hypothesized that VL activity would be reduced when the

subjects wore the knee brace compared to when they did not. We further hypothesized

that this would occur regardless of the type of exercise (OKC versus CKC). However,

this did not occur, as no differences were observed between the braced and unbraced

conditions when comparing the VL activity during both the OKC and CKC exercises.

Unlike the VM, the greatest VL activity occurred when the knee was extending

from 90 to 450 of flexion. When the type of exercise was compared, VL activity was

greatest during the OKC exercise. This was observed during the final 450 of extension

concentrically and eccentrically. However, when the knee was in a more flexed position

the eccentric activity was greater during the CKC exercise.

Patellofemoral Bracing

The concept behind the present study was similar to a study conducted by Gulling

et a121 that investigated the effect of patellar bracing on quadriceps EMG activity during

isokinetic exercise. However, the results of the present study are in contrast to their

results. Gulling et al.21 reported significantly greater EMG readings in subjects

performing isokinetic exercises during a non-braced condition versus a braced condition.

In the present study, we observed significantly greater quadriceps EMG activity when the

patellar brace was worn (Figure 5-1).





























Figure 5-1. VM EMG activity during braced conditionsignificantly greater than the
Unbraced Condition (P < 0.05)

The significant decrease in quadriceps EMG activity after the application of the

brace was thought by Gulling et al21 to induce a weaker muscle contraction reducing

abnormal patellar tracking and decreasing symptoms of patellofemoral pain syndrome

(PFPS). The conflicting results may be attributed to the type of subjects and the exercise

protocol utilized in each study. Gulling et al.21 used subjects who were suffering from

patellofemoral pain at the time of the study and they performed only an isokinetic OKC

exercise protocol. In the present study, only healthy subjects were used and they

completed both an OKC exercise (knee extension) and a CKC exercise (leg press)

protocol. Healthy subjects were chosen to examine if the application of the brace would

have a similar effect on the quadricep muscle activity of individuals without

patellofemoral pain. The results may suggest that healthy subjects respond differently to

the patellofemoral brace application compared to subjects with patellofemoral pain. The

CKC exercise (leg press) was used to incorporate a functional aspect, and a CKC exercise

(knee extension ) was used to assess the efficacy of a frequently used rehabilitation tool.


VM

1.6
1.4
1.2
1
O m Unbraced
m 0.8
uw 0.U6 Braced

0.4
0.2
0
Braced Condition









These exercises are very different from an isokinetic exercise. It is possible that the fixed

speed with the isokinetic exercise may have produced different EMG readings seen in the

Gulling et al.21 study. A metronome was utilized in the current study in an attempt to

control for speed alterations during the exercise. The subjects in the existing study may

have deviated slightly from the constant speed that was set by the metronome, therefore

producing different results. In addition, the brace applied pressure on the EMG surface

electrodes, which may have caused higher EMG activity readings during the braced

condition compared to the non-braced condition. Gel from the surface electrodes was

observed around the area after brace application, which may suggest more topical

pressure on the electrodes compared to the non-braced condition. This possible

limitation was not noted in the study conducted by Gulling et al.21 The inability to

allocate an accommodation period to the patellofemoral knee brace has been mentioned

as a limitation in the present study. The previous studies that examined the effects of

knee bracing on muscle activation also failed to examine the idea of an accommodation

period.21'41 It is possible that muscle activation was affected by the application of the

knee brace, which was not controlled for through an accommodation period.

A previous study by Ostemig and Robertson41 examined the effects of prophylactic

knee bracing on lower extremity joint position and muscle activation during running.

The results of this study revealed a significant reduction of EMG activity in73% of the

subjects with the braced condition compared to the non-braced condition. The results of

this study were also in contrast with the present study. Unlike the present study, Osternig

and Robertson41 used a knee brace with a polyaxial hinge instead of a patella stabilizing

brace. They also utilized a running protocol instead of a CKC and OKC exercise









protocol. In both studies EMG activity was assessed. The running protocol was

completed on a treadmill, possibly producing different EMG activity patterns compared

to the leg press and knee extension exercise done in the present study. The leg press and

the knee extension exercises were done at 75% of the subject's 1-RM. It is likely that

this would produce an overall higher EMG readings, resulting in the differences found

between the studies. In addition to the differences stated, Osternig and Robertson41

incorporated only 6 subjects in their study. This limited number may have affected the

statistical significance that was seen during the braced condition. The present study

included 23 subjects who all performed both exercises with and without the

patellofemoral brace. The adequate number of subjects increases the statistical power of

the present study reinforcing the significant differences found.

Patellofemoral Taping

Another treatment often incorporated in a rehabilitation protocol for patellofemoral

pain is patellofemoral taping. The studies conducted on this treatment can be compared

to the investigations mentioned above as well as the present study, because of the

mechanisms that influence patellar tracking. Both the patellar brace and patellar taping

attempt to aid the patella in proper tracking through the trochlear groove.

Kowall et al.28 studied patellar taping in the treatment of patellofemoral pain. VM

and VL activity was assessed during a CKC step-up and step-down exercise using surface

EMG electrodes. This study revealed an increase in EMG activity over time during a

rehabilitation program that utilized patellar taping.28 The results of this study would be

similar to the present study if the increase in EMG activity was seen immediately after

the patellar tape was applied. The change in the EMG activity seen by Kowall et al.28

was not noted until later in the rehabilitation protocol, which limits the comparison that









can be made to the present study. The effect of patellar taping on pain and

neuromuscular performance was studied in subjects with patellofemoral pain by Ng and

Cheng.40 Their results indicated that patellar taping significantly decreased

patellofemoral pain and VMO to VL EMG ratio. The VMO was found to be less active

with the patellar tape, which is in contrast to the results of the current study.40 Unlike the

present study, Ng and Cheng40 used subjects that presented with patellofemoral pain.

The subjects used in the current study had no history of previous knee pain.

The major difference between patellofemoral taping and patellofemoral bracing

that needs to be considered is the placement of the device on the skin. The

patellofemoral tape is normally based on the McConnell34 taping technique. This

technique involves the application of tape only over the patella to aid in patellar tracking

through the trochlear groove. Patellofemoral bracing encompasses the entire knee area,

leaving the patella free, with a buttress surrounding the patella to aid in patellar tracking.

The pressure of the brace on the quadricep muscle group may explain the increased EMG

activity found with brace application in the present study. This increase in pressure

caused by the patellofemoral brace is not seen with the use of patellofemoral taping.

Exercise Comparison

The results observed regarding the phase of exercise and exercise type are

important to note although these results did not directly relate to the hypotheses of the

present study. Unlike the previous studies mentioned, the results of the present study

were very similar to results found in studies that investigated OKC and CKC exercises

with EMG. A recent study done by Clements et al9 compared quadriceps EMG activity

during OKC and CKC exercises. The EMG activity was collected during an isometric

contraction using the leg press and the knee extension machine at 300, 600, and 900 of










flexion. The results revealed that the OKC exercise had significantly higher EMG

activity at 300 of knee flexion when compared to the CKC exercise at 300. The current

study revealed similar results as the second phase of the concentric contraction (450 to 0

of knee flexion) was significantly greater in the OKC compared to the CKC (Figure 5-2).

However, the second phase of the eccentric contraction (450 to 900 of knee flexion) was

significantly greater in the CKC as compared to the OKC in the present study (Figure 5-

3). Similar to these findings, Clements et al.9 reported significantly higher EMG activity

in the CKC exercises at 600 and 900 of knee flexion compared to the OKC exercises in

the same ranges. The results for the present study were reported regardless of the braced

condition. A knee brace was not used in the Clements et al.9 investigation.


Con 45 to 0 degrees of knee flexion

0.9
0.8 -
0.7
0.6
E 0.5 +OKC
M 0.4 -- CKC
LU
0.3
0.2
0.1
0
1 2
Exersice Type



Figure 5-2. Concentric 450 to 0 of knee flexion during CKC and OKC exercises
significant interaction (P < 0.05)











Ecc 45 to 90 degrees of knee flexion

1.2
1
> 0.8 -
--.- -_-_-.--, CKC
0.6
0 -.- OKC
M 0.4 -
0.2
0 -
1 2
Exercise Type


Figure 5-3. Eccentric 450 to 900 of knee flexion during CKC and OKC exercises
significant interaction (P < 0.05)

Escamilla et al.17 also conducted a study that revealed comparable results to the

present study. The OKC exercises produced significantly greater quadriceps EMG

activity between 15-650 of knee flexion and the CKC exercises produced significantly

greater quadriceps EMG activity at knee angles greater than 83. These results are

similar to the current study as well as the study conducted by Clements et al.9. The

similarities among the studies are important to mention. Although the present study

produced different EMG activity than previous studies that investigated patellofemoral

bracing, the basic muscle activity of the quadriceps has been seen in multiple earlier

studies.

The results regarding the phase of exercise are also important to notice. The

ANOVAs for both the VM and VL revealed significant interactions between phase of

exercise. The EMG activity for the VM was greater during the concentric phase of

motion, compared to the eccentric phase. However, the difference was not statistically









significant. The EMG activity during the VL's concentric phase of motion was

significantly greater than the eccentric phase. These results can be compared to a study

conducted by Kellis and Baltzopoulos26 on muscle activation differences between

eccentric and concentric isokinetic exercise. The results of this study revealed greater

EMG activity during the concentric motion compared to the eccentric motion.

Kellis and Baltzopoulos26 used an isokinetic dynamometer without a knee brace,

whereas the present study utilized the knee extension and leg press machines with and

without a patellofemoral knee brace. In the present study, the results for the phase of

motion were reported in combination of both the braced and non-braced conditions.

Although the study protocols were different they produced similar EMG activity readings

for the VM and VL.

Clinical Implications

Many studies have verified the prevalence of patellofemoral pain as the most

common clinical condition presented to clinicians who treat musculoskeletal conditions.59

The exact cause of this syndrome is not clear, and varies from patient to patient. The

present study was an investigation into one of the many methods used to treat

patellofemoral pain.

The results of this study suggest that quadriceps muscle activation increases with

the application of a patellofemoral knee brace. These results would support the use of a

patellofemoral brace during a rehabilitation protocol for patellofemoral pain. However, it

is important to be aware of the circumstances of the study protocol. Only healthy

subjects who had no previous history of knee pain participated in the study, therefore

subjects who have patellofemoral pain may respond differently to the knee brace as

suggested by Gulling et al.21 The conflicting results between the current study and the









study conducted by Gulling et al.21 suggests that rehabilitation specialists treat with

caution when utilizing a knee brace as part of a rehabilitation protocol.

Although a significant interaction was not revealed between the type of exercise,

the braced condition, and the phase of exercise, it is important to note that the results did

follow the trend observed in previous studies.

Summary

Patellofemoral pain is the most frequent musculoskeletal disorder involving the

knee seen in sports medicine clinics.3'44 The prevalence of this syndrome has lead to

extensive research in the area of rehabilitation. Many studies have been conducted

advocating the use of a patellofemoral brace in either prevention or treatment of

patellofemoral pain.4'31,49 Of the studies conducted on patellofemoral bracing, only one

investigated the effect of the brace on quadriceps muscle activation.21 The purpose of the

present study was to assess the effect of a patellofemoral knee brace on quadriceps

muscle action.

Twenty-three subjects with no previous history of knee pain were utilized in the

current study to evaluate a healthy subject's response to a patellofemoral brace. Each

subject performed OKC and CKC exercises with and without a patellofemoral knee

brace. Surface EMG was utilized to assess quadriceps muscle activity during each

exercise and braced condition. The data were analyzed to identify interactions.

The data analysis demonstrated a significant increase in EMG activity of the

quadriceps when the patellofemoral brace was applied, regardless of the exercise type.

The results did not indicate a significant interaction between the type of exercise, the

braced condition, and the phase of exercise. These results indicated that when the type of

exercise is considered, OKC and CKC, there is no significant difference in the braced and









unbraced conditions. The results of this study and the conflicting conclusions to the

Gulling et al.21 investigation call for more extensive research on patellofemoral bracing

and the effect of the brace on quadriceps muscle activity.

Implications for Future Research

The results of this study suggest a need for future research in the area of

patellofemoral bracing. This study is the first known study to investigate patellofemoral

bracing on quadriceps activity during OKC and CKC exercises. Previous investigations

studied subjects with patellofemoral pain using an isokinetic dynamometer.21

It is evident that a more extensive investigation is needed into the effects of a

patellofemoral knee brace on quadriceps muscle activity. Future research should

consider subjects with and without patellofemoral pain as well as OKC and CKC exercise

protocols. This would allow a comparison to be made between the patellofemoral pain

group and the non-injured group.

Future studies examining the effect of patellofemoral bracing on quadriceps activity

should consider an accommodation period for the patellofemoral brace. This

accommodation period would control for any immediate muscle activation differences

that may be present with brace application. This added control may allow for more

reliable results.

Another aspect that may be considered during future investigations is the use of

fine wire EMG. Fine wire EMG would decrease the effect that the surface EMG may

have had on the results of the present study. The pressure applied to the surface EMG

electrodes with the brace application may be eliminated with the use of fine wire EMG,

therefore adding to the validity of the results.














APPENDIX A
UNIVERSITY OF FLORIDA INSTITUTIONAL REVIEW BOARD

1. TITLE OF PROTOCOL:

The effect of a patellofemoral knee brace on quadriceps activity.


2. PRINCIPAL INVESTIGATOR:

Madelon C. Haskin, ATC-L
2502 NW 16th Avenue
Gainesville, FL 32605
Home: (352) 378-1337
Cell: (352) 235-0101
haskin02@hotmail.com


3. SUPERVISORS

Dr. Michael Powers, Ph.D., Assistant Professor, Athletic Training
University of Florida
144 Florida Gym
P.O. Box 118205
(352) 392-0580 ext. 1332
mpowers@hhp.ufl.edu


4. DATES OF PROPOSED PROTOCOL:

From February 15, 2003 to February 15, 2004

5. SOURCE OF FUNDING FOR THE PROTOCOL:

Unfunded









6. SCIENTIFIC PURPOSE OF THE INVESTIGATION:

Patellofemoral pain is a common phenomenon in the physically active, and the
patellofemoral knee brace is frequently advocated in rehabilitation protocols. The effect
of the knee brace on the activation of the quadriceps muscles has not been thoroughly
researched. This study may give professionals in the field of rehabilitation a better
understanding of what is happening when their athlete applies a patellofemoral knee
brace. This study will attempt to add to this knowledge base, thereby assisting
rehabilitation specialists in precise programs to allow athletes to return to activity faster
and with better long-term results.


7. DESCRIBE THE RESEARCH METHODOLOGY IN NON-
TECHNICAL LANGUAGE:

The purpose and procedures of the study will be explained to each subject and they will
be asked to read and sign an Informed Consent. Once the forms have been completed
and consent is given, the subjects will have their one repetition maximum assessed for the
leg extension and leg press exercises. This involves beginning with a very lightweight
for each exercise and progressing until a weight is reached that cannot be lifted one time.
We will be using the protocol recommended by the National Strength and Conditioning
Association. The subjects will then be asked to return at least 48 hours after their first
day and will have one spot on their medial quadriceps (VMO) and one spot on their
lateral quadriceps (VL) cleaned with isopropyl rubbing alcohol and any hair in those two
places shaved off. Surface electromyography electrodes will be placed on these two
areas to record muscle activity of the quadriceps muscles. Prior to performing the next
tasks, the subject will warm up for 3 minutes on an exercise bike. The subjects will then
perform one maximal effort for each exercise using the maximum weight obtained from
the first session. The EMG measurements collected by this contraction will be used to
normalize the data of the other exercises. Once this is complete the subject will then
perform five repetitions of each exercise using 85% of the maximum weight obtained
from session one. Each exercise will be performed twice, once while wearing a
patellofemoral knee brace and again without the patellofemoral knee brace. The order of
the exercises and the order of bracing (or not) will be randomly assigned. Quadriceps
muscle activity will be recorded during the 5 repetitions of each exercise performed by
the subject. There will be 5 minutes of rest between each testing condition.
Measurements of subjects' performances on all the tasks will be coded and analyzed in an
anonymous fashion to maintain subject confidentiality.

8. POTENTIAL BENEFITS AND ANTICIPATED RISK

The data collected may not directly benefit the subjects involved in the study. The study
may ultimately benefit people with patellofemoral pain by facilitating a faster return to
activity. Subjects performing some of the tasks for the first time may be at risk of injury
due to unfamiliarity of the tasks or equipment. Consistently following proper set-up
procedures and performing several practice trials for each task should minimize this risk.









A National Athletic Trainers Association licensed athletic trainer (ATC/L) who will
assess and treat any injuries that may occur will be present for all exercise and testing
sessions.


9. DESCRIBE HOW PARTICIPANTS WILL BE RECRUITED, THE
NUMBER AND AGE OF THE PARTICIPANTS, AND PROPOSED
COMPENSATION:

Participants will be recruited from courses taught within the College of Health
and Human Performance. The principle investigator will asked the instructors permission
before recruiting subjects. No student will be recruited from any class taught by the
principal investigator. All subjects will be informed by the principal investigator as to
what the study is investigating. A total of 24 voluntary subjects will be recruited.
Subjects will range in age from 18-30 years. Subjects who have had knee surgery of any
type, and subjects who have a history of knee pain other than anterior knee pain will be
excluded from the study. There will be no direct compensation for any subject.


10. DESCRIBE THE INFORMED CONSENT PROCESS:

To ensure the subject's voluntary, affirmative agreement to participate in the study
informed consent will be obtained prior to any testing. A subject coding system will be
used to protect each subject's confidentiality. Subjects will be assured that they may
withdraw from the study at any time with no consequence.




Principal Investigator


Principal Investigators' Signature Date


Supervisor


Supervisors' Signature Date

I approve this protocol for submission to the UFIRB:


Department Chairs' Signature


Date














APPENDIX B
INFORMED CONSENT

Protocol Title: The effects of a patellofemoral knee brace on quadriceps muscle
activation.

Please read this consent document carefully before you decide to participate in this study.

Purpose of the research study:
The purpose of this research study is to determine the effects of a knee brace on thigh
(quadriceps) muscle contraction using surface electromyography (a device that measures
muscle activity).

What you will be asked to do in the study:
You will be asked to report for two testing times. The fist testing time will be to
determine how much weight you can lift one time on a leg press and a leg extension
exercise machine. Before doing this, you will first warm up by riding a stationary bicycle
for three minutes. You will then perform five repetitions on the leg press machine with a
very lightweight. The weight will continuously be increased and you will be asked to lift
it one time. This will continue until we reach a weight you are unable to lift. After a
five-minute rest you will be asked to repeat the same procedure on the leg extension
machine. For the leg extension, you will only use the non-dominant leg (the one you not
normally kick a ball with). You will be asked to return for the second session at least 48
hours later. At that time, your non-dominant leg will be prepped and five adhesive
electrodes will be placed on the skin of your thigh muscles. If necessary a small area of
skin will be shaved to allow for electrode placement and the skin will be cleaned with
alcohol. These electrodes allow us to measure the muscle activity (how much it
contracts) when you exercise. They only collect or read the electrical activity of the
muscle, thus they do not transmit an electrical current into your body. You will be asked
to lift the maximum weight obtained from the first session one time for each exercise.
After that, you will be asked to lift a portion (85%) of the weight from the first day three
times each, doing each exercise two times. One of the times you do the exercises you
will be asked to wear the knee brace, the order is determined by chance. Your quadriceps
muscle function will be recorded during each of the exercises. Once you are done with
the second day of testing you have completed the study. If you have had knee surgery of
any type or if you have a history of knee pain other than anterior knee pain you will not
be included in the study.

Time required:
First testing session: 20 minutes
Second testing session: 1 hour and 30 minutes









Risks and Benefits:
There are no direct benefits from your participation in this study. You may have some
mild leg muscle soreness 24-48 hours following the study. As with any type of exercise,
there is a slight risk of musculoskeletal injury such as a sprain or a muscle pull. A
certified athletic trainer will be present to evaluate and treat any such injuries should they
occur.

Compensation:
There is no compensation for your participation in this study.

Confidentiality:
Your identity will be kept confidential to the extent provided by law. Your information
will be assigned a code number. The list connecting your name to this number will be
kept in a locked file in my faculty supervisor's office. When the study is completed and
the data have been analyzed, the list will be destroyed. Your name will not be used in any
report.

Voluntary Participation:
Your participation in this study is completely voluntary. There is no penalty for not
participating.

Right to withdraw from the study:
You have the right to withdraw from the study at anytime without consequence.

Whom to contact if you have questions about the study:
Carol Haskin, Graduate student, Department of Exercise and Sport Sciences
(352) 235-0101

Dr. Michael Power, Ph.D., Assistant Professor, Department of Exercise and Sports
Sciences
(352) 392-0584 x1332

Whom to contact about your rights as a research participant in the study:
UFIRB Office, Box 112250, University of Florida, Gainesville, FL 32611-2250;
Phone number: 392-0433.

Agreement:
I have read the procedure described above. I voluntarily agree to participate in the
procedure and I have received a copy of this description.

Participant: Date:


Principal Investigator:


Date:















APPENDIX C
DATA SHEET

DATE

ID #

Leg tested R / L

Size of Brace S /M / L / XL

Gender M / F

Age

Height

Weight

1-RM Knee Extension 75% KE

1-RM Leg Press 75% LP



Order of Conditions:

















APPENDIX D
ANOVA TABLES


Table E-1. ANOVA test results for
Source Sum of Squares
Exercise .152
Error 4.014


Braced
Error

Phase of Ex
Error

Ex*Brace
Error

Ex*Phase
Error

Brace*Phase
Error


.342
1.482

5.137
1.685

.164
1.058

4.057
1.496


Ex*Brac*Ph .0239
Error .682
Table E-2. ANOVA test results for
Source Sum of Squares
Exercies 1.632
Error 3.679


Braced
Error

Phase of Ex
Error

Ex*Brace
Error

Ex*Phase
Error

Brace*Phase
Error

Ex*Brac*Ph
Error


.0438
.855

2.474
1.243

.0643
.593

4.505
1.317

.0182
.317

.0057
.524


Mean Square
.152
.182


F
.836


5.082


67.075


3.417


59.67


4.917


.772



F
9.756


1.128


43.778


.024


75.24


.750


.342
.0674

1.712
.0255

.164
.0481

1.352
.0227

.0356
.0723


.0798
.0103

Mean Square
1.632
.167


.0438
.0389

.825
.0188

.0643
.0269

1.502
.0199

.0036
.0048

.0019
.0079


Significance
.371


.034


.000


.078


.000


.514



Significance
.005


.300


.000


.879


.000


.526















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BIOGRAPHICAL SKETCH

I was born on August 2, 1979, in Charlotte, North Carolina to Edward and Julia

Haskin. I grew up the younger sister of Eric Franklin on Markwell Drive in Matthews,

North Carolina. This is the place where my parents continue to live and I still call home.

I attended Matthews Elementary School and during this time I developed a love of

sports by becoming active in tee-ball, coach pitch, and softball, and I also played the

piano. I attended Randolph Junior High School from seventh to ninth grade. I began

involvement with track in seventh grade and continued my love of softball, and piano.

Providence Senior High School is where I spent my tenth through twelfth grade years. I

became very active in cross-country, indoor track, outdoor track, and softball during high

school. My interest in sports medicine began during this time.

After graduating high school in 1997, I continued my education at the University of

North Carolina at Chapel Hill. I began to expand my interest in sports medicine during

my sophomore year and was accepted into the Athletic Training Program as a junior. I

worked as a student athletic trainer with various men and women's collegiate teams as

well as at a local high school. I graduated from UNC-Chapel Hill in May of 2001 with a

Bachelor of Arts degree in exercise and sports science.

I began work on my master's degree in August of 2001 at the University of Florida.

While at UF I worked as a graduate assistant at Hawthorne High School in the local

Gainesville area. My quest for a master's thesis began during this time.