Patellofemoral disorders: A classification system and clinical guidelines for nonoperative rehabilitation

Journal of Orthopaedic and Sports Physical Therapy

Volumn 28, Issue 5, 1998, Pages 307-322

  Wilk, Kevin E ^a,b,c   Davies, George J ^d,e   Mangine, Robert E ^f   Malone, Terry R ^g  

^a HealthSouth Corporation   (United States)

^b AMERICAN SPORTS MEDICINE INSTITUTE   (United States)

^c MARQUETTE UNIVERSITY   (United States)

^d UNIVERSITY OF WISCONSIN LA CROSSE   (United States)

^e GUNDERSEN LUTHERAN MEDICAL CENTER   (United States)

^f Kentucky Rehabilitation Services   (United States)

^g UNIVERSITY OF KENTUCKY   (United States)

Author keywords

Classification; Patellofemoral dysfunction; Rehabilitation

Indexed keywords

ARTHROPATHY; BIOMECHANICS; COMPRESSION; DISEASE CLASSIFICATION; HUMAN; JOINT INJURY; JOINT INSTABILITY; NEUROLOGIC DISEASE; ORTHOPEDIC SURGERY; OSTEOCHONDRITIS; OSTEOCHONDRITIS DISSECANS; PATELLA DISLOCATION; PATELLOFEMORAL JOINT; PRACTICE GUIDELINE; REPETITIVE STRAIN INJURY; REVIEW; SOFT TISSUE INJURY; SPORTS MEDICINE; SUBLUXATION; SYMPATHETIC DYSTROPHY;

EID: 0031735565     PISSN: 01906011     EISSN: None     Source Type: Journal    
DOI: 10.2519/jospt.1998.28.5.307     Document Type: Review

References (139)

1. Adler N, Perry J, Kent B, Robertson K: Electromyography of the vastus medialis oblique and vastus lateralis in normal subjects during gait. Electromyogr Clin Neurophysiol 23(7):643-649, 1983
2. Arroll B, Ellis-Pegler E, Edwards A, Sutcliffe G: Patellofemoral pain syndrome: A critical review of the clinical trials on nonoperative therapy. Am J Sports Med 25(2):207-212, 1997
3. Beckman M, Craig R, Lehman RC: Rehabilitation of patellofemoral dysfunction in the athlete. Clin Sports Med 8(4):841-860, 1989
4. Bennett JC, Stauber WT: Evaluation and treatment of anterior knee pain using eccentric exercise. Med Sci Sports Exerc 18(5):526-530, 1986
5. Bentley G, Dowd G: Current concepts of etiology and treatment of chondromalacia patella. Clin Orthop 189:209-228, 1984
6. Blackburn TA, Eiland G, Bandy WD: An introduction to the plica. J Orthop Sports Phys Ther 3(4):171-177, 1982
7. Blazina ME, Kerlan RK, Jobe FW, Carter VS, Carlson GJ: Jumper's knee. Orthop Clin North Am 4(3):665-678, 1973
8. Bockrath K, Wooden C, Worrell T, Ingersoll CD, Farr J: Effects of patella taping on patella position and perceived pain. Med Sci Sports Exerc 25(9):989-992, 1993
9. Bose K, Kanagasuntheram R, Osman MBH: Vastus medialis oblique: An anatomic and physiological study. Orthopedics 39:880-883, 1980
10. Brunet ME, Stewart GW: Patellofemoral rehabilitation. Clin Sports Med 8(2):319-329, 1989
11. Callaghan MJ, Oldham JA: The role of quadriceps exercise in the treatment of patellofemoral pain syndrome. Sports Med 21(5):384-391, 1996
12. Cerny K: Vastus medialis oblique/vastus lateralis muscle activity ratios for selected exercises in persons with and without patellofemoral pain syndrome. Phys Ther 75(8):672-683, 1995
13. Cherf J, Paulos L: Bracing for patellar instability. Clin Sports Med 9(4):813-821, 1990
14. Clancy WG: Tendon trauma and overuse injuries. In: Leadbetter WB, Buckwalter VA, Gordon SL (eds), Sports-Induced Inflammation: Clinical and Basic Science Concepts, pp 609-618. Park Ridge, IL: American Academy of Orthopaedic Surgeons, 1990
15. Conway A, Malone TR, Conway R: Patellar alignment/tracking alteration: Effect on force output and perceived pain. Isokin Exerc Sci 2(1):9-17, 1992
16. Cooper DE, DeLee JD, Ramamurthy S: Reflex sympathetic dystrophy of the knee. Treatment using continuous epidural anesthesia. J Bone Joint Surg 71A(3):365-369, 1989
17. Crosby EB, Insall J: Recurrent dislocation of the patella. Relation of treatment to osteoarthritis. J Bone Joint Surg 58A(1):9-13, 1976
18. DeHaven KE, Dolan WA, Mayer PJ: Chondromalacia patella in athletes. Clinical presentation and conservative management. Am J Sports Med 7(1):5-11, 1979
19. Doucette SA, Child DD: The effect of open and closed chain exercise and knee joint position of patellar tracking in lateral patellar compression syndrome. J Orthop Sports Phys Ther 23(2):104-110, 1996
20. Doucette SA, Goble EM: The effect of exercise on patellar tracking in lateral patellar compression syndrome. Am J Sports Med 20(4):434-440, 1992
21. Dye SF: The pathophysiology of patellofemoral pain. Presented at the 48th annual National American Trainers Association Meeting, Salt Lake City, UT, June 19, 1997
22. Edmonson AS, Crenshaw AH (eds): Campbell's Operative Orthopaedics, St. Louis, MO: Mosby, 1980
23. Eng JJ, Pierrynowski MR: Evaluation of soft foot orthotics in the treatment of patellofemoral pain syndrome. Phys Ther 73:62-70, 1993
24. Ficat RP, Hungerford DS: Disorders of the Patellofemoral Joint, Baltimore, MD: Williams & Wilkins, 1977
25. Ficat RP, Phillippe J, Hungerford DS: Chondromalacia patellae: A system of classification. Clin Orthop 144:55-62, 1979
26. Finestone A, Radin EL, Lev B, Shlamkovitch N, Wiener M, Milgrom C: Treatment of overuse patellofemoral pain. Prospective randomized controlled clinical trials in a military setting. Clin Orthop 293:208-210, 1993
27. Fisher RL: Conservative treatment of patellofemoral pain. Orthop Clin North Am 17(2):269-272, 1986
28. Fitzgerald CK, McClure PW: Reliability of measurements obtained with four tests for patellofemoral alignment. Phys Ther 75(2):84-92, 1995
29. Fox TA: Dysplasia of the quadriceps mechanism: Hypoplasia of the vastus medialis muscle as related to the hypermobile patella syndrome. Surg Clin North Am 55(1):199-226, 1975
30. Fulkerson JP: Disorders of patellofemoral joint: Evaluation and treatment. Presented at the Evaluation and Treatment of Injured Athletes Course, Boston University, Cape Cod, MA, July 29, 1993
31. Fulkerson JP (ed): Disorders of the Patellofemoral Joint (3rd Ed), Baltimore, MD: Williams & Wilkins, 1997
32. Fulkerson JP: The etiology of patellofemoral pain in young active patients: A prospective study. Clin Orthop 179:129-133, 1983
33. Fulkerson JP: Evaluation of peripatellar soft tissues and retinaculum in patients with patellofemoral pain. Clin Sports Med 8(2):197-202, 1989
34. Fulkerson JP, Hungerford DS: Disorders of the Patellofemoral Joint (2nd Ed), Baltimore, MD: Williams & Wilkins, 1990
35. Fulkerson JP, Kalenak A, Rosenberg TD, Cox JS: Patellofemoral pain. Instru Course Lect 41:57-71, 1992
36. Fulkerson JP, Schutzer SF: After failure of conservative treatment of painful patellofemoral malalignment: Lateral release or realignment? Orthop Clin North Am 17(2):283-288, 1986
37. Fulkerson JP, Shea KP: Disorders of patellofemoral alignment. J Bone Joint Surg 72A(9):1424-1429, 1990
38. Fulkerson JP, Tennant R, Jaivin JS, Grunnet M: Histological evidence of retinacular nerve injury associated with patellofemoral malalignment. Clin Orthop 197:196-205, 1985
39. Fyfe I, Stanish WD: The use of eccentric training and stretching in the treatment and prevention of tendon injuries. Clin Sports Med 11(3):601-624, 1992
40. Gerrard B: The patellofemoral pain syndrome: A clinical trial of the McConnell programme. Aust J Physiother 35:71-80, 1989
41. Grabiner MD, Koh TJ, Draganich LF: Neuromechanics of the patellofemoral joint. Med Sci Sports Exerc 26(1):10-21, 1994
42. Grabiner MD, Koh TJ, Miller GF: Fatigue rates of vastus medialis oblique and vastus lateralis during static and dynamic knee extension. J Orthop Res 9(3):391-397, 1991
43. Grana WA, Kriegshauser LA: The scientific basis of extensor mechanism disorders. Clin Sports Med 4(2):247-257, 1985
44. Greenwald AE, Bagley AM, France EP, Paulos LE, Greenwald RM: A biomechanical and clinical evaluation of a patellofemoral knee brace. Clin Orthop 324:187-195, 1996
45. Grelsamer RP: Classification of patellofemoral disorders. Am J Knee Surg 10(2):96-100, 1997
46. Grelsamer RP: Patellofemoral semantics. The Tower of Babel. The International Patellofemoral Study Group. Am J Knee Surg 10(2):92-95, 1997
47. Gruber MA: The conservative treatment of chondromalacia patellae. Orthop Clin North Am 10(1):105-115, 1979
48. Gryzlo SM, Patek RM, Pink M, Perry J: Electromyographic analysis of knee rehabilitation exercises. J Orthop Sports Phys Ther 20(1):36-43, 1994
49. Gulling LK, Lephart SM, Stone DA, Irrgang JJ, Pincivero DM: The effect of patellar bracing on quadriceps EMG activity during isokinetic exercise. Isokin Exerc Sci 6(2):133-138, 1996
50. Hanten WP, Schulthies SS: Exercise effect on electromyographic activity of the vastus medialis oblique and vastus lateralis muscles. Phys Ther 70(9):561-565, 1990
51. Hawkins RJ, Bell RH, Anisette G: Acute patellar dislocation. The natural history. Am J Sports Med 14(2):117-120, 1986
52. Henry JH: Conservative treatment of the patellofemoral subluxation. Clin Sports Med 8(2):261-278, 1989
53. Hodges PW, Richardson CA: The influence of isometric hip adduction on quadriceps femoris activity. J Rehabil Med 25(2):57-62, 1993
54. Hoffa A: The influence of the adipose tissue with regard to the pathology of the knee. J Am Med Assoc 43:795-799, 1914
55. Horwitz J: Recurrent or habitual dislocations of the patella. J Bone Joint Surg 19A:1027-1031, 1937
56. Huberti HH, Hayes WC: Patellofemoral contact pressures. J Bone Joint Surg 66A(5):715-724, 1984
57. Hughston JC: Subluxation of the patella. J Bone Joint Surg 50A(5):1003-1026, 1968
58. Hughston JC, Stone M, Andrews JR: The suprapatellar plica. Its role in internal derangement of the knee. J Bone Joint Surg 55A(6):1318-1323, 1973
59. Hughston JC, Walsh WM, Puddu G: Patellar Subluxation and Dislocation, Philadelphia: W.B. Saunders Company, 1984
60. Hungerford DS, Barry M: Biomechanics of the patellofemoral joint. Clin Orthop 144:9-15, 1979
61. Ingersoll CD, Knight KL: Patellar location changes following EMG biofeedback or progressive resistive exercises. Med Sci Sports Exerc 23(10):1122-1127, 1991
62. Insall J: "Chondromalacia patellae"; Patellar malalignment syndrome. Orthop Clin North Am 10(1):117-127, 1979
63. Insall J: Current concepts review: Patella pain. J Bone Joint Surg 64A(1):147-152, 1982
64. Jackson RW, Marshall DJ, Fujisawa Y: The pathologic medial shelf. Orthop Clin North Am 13(2):307-312, 1982
65. Jensen K, DiFabio RP: Evaluation of eccentric exercise in treatment of patellar tendinitis. Phys Ther 69(3):211-216, 1989
66. Johnson DP, Eastwood DM, Witherow PJ: Symptomatic synovial plica of the knee. J Bone Joint Surg 75A(10):1485-1496, 1993
67. Kajala UM, Aalto T, Osterman K, Dahlstrom S: The effect of Volleyball playing on the knee extensor mechanism. Am J Sports Med 17(6):766-769, 1989
68. Kannus P, Niitymake S: Which factors predict outcome in the nonoperative treatment of patellofemoral pain syndrome? A prospective follow-up study. Med Sci Sports Exerc 26(3):289-296, 1994
69. Karst GM, Jewett PD: Electromyographic analysis of exercises proposed for differential activation of medial and lateral quadriceps femoris components. Phys Ther 73(5):286-295, 1993
70. Karst GM, Willett GM: Onset timing of electromyographic activity in the vastus medialis oblique and vastus lateralis muscles in subjects with and without patellofemoral pain syndrome. Phys Ther 75(8):811-823, 1995
71. Katz MM, Hungerford DS: Reflex sympathetic dystrophy affecting the knee. J Bone Joint Surg 69B(5):797-803, 1987
72. Klingman RE, Liaos SM, Hardin KM: The effect of subtalar joint posting on patellar glide position in subjects with excessive rearfoot pronation. J Orthop Sports Phys Ther 25(3):185-191, 1997
73. Knight KL: Rehabilitating chondromalacia patella. Physician Sportsmed 7(10):147-148, 1979
74. Kottke FJ, Davley DL, Ptak RA: The rationale for prolonged stretching for correction of shortening of connective tissue. Arch Phys Med Rehabil 47:345-352, 1996
75. Kowall MG, Kolk G, Nuber GW, Cassisi JE, Stern SH: Patellar taping in the treatment of patellofemoral pain: A prospective randomized study. Am J Sports Med 24(1):61-66, 1996
76. Kramer PG: Patella malalignment syndrome: Rationale to reduce excessive lateral pressure. J Orthop Sports Phys Ther 8(6):301-309, 1986
77. LaBrier K, O'Neill DB: Patellofemoral stress syndrome: Current concepts. Sports Med 16(6):449-459, 1993
78. Larsen B, Andreasen E, Urfer A, Mickelson MR, Newhouse KE: Patellar taping: A radiographic examination of the medial glide technique. Am J Sports Med 23(4):465-471, 1995
79. Larson RL, Cabaud HE, Slocum DB, James SL, Keenan T, Hutchison T: The patellar compression syndrome: Surgical treatment by lateral release. Clin Orthop 134:158-167, 1978
80. Laurin CA, Dassault R, Levesque HP: The tangential X-ray investigation of the patellofemoral joint: X-ray technique, diagnostic criteria and their interpretation. Clin Orthop 144:16-26, 1979
81. LeVeau BF, Rogers C: Selective training of the vastus medialis muscle using EMG biofeedback. Phys Ther 60(11):1410-1415, 1980
82. Levine J: Chondromalacia patellae. Physician Sportsmed 7:40-43, 46-49, 1979
83. Levine J: A new brace for chondromalacia patella and kindred conditions. Am J Sports Med 6(3):137-139, 1978
84. Levine J, Splain S: Use of the infrapatellar strap in the treatment of patellofemoral pain. Clin Orthop 139:179-181, 1979
85. Lieb FJ, Perry J: Quadriceps function: An anatomical and mechanical study using amputated limbs. J Bone Joint Surg 50A(8):1535-1548, 1968
86. Lieb FJ, Perry J: Quadriceps function: An electromyographic study under isometric conditions. J Bone Joint Surg 53A(4):749-758, 1971
87. Lidenfeld TN, Bach BR, Wojtys EM: Reflex sympathetic dystrophy and pain dysfunction in the lower extremity. J Bone Joint Surg 78A:1936-1944, 1996
88. Light LE, Nuzik S, Personius W, Barstrom A: Low load prolonged stretch versus high load in treating knee contractures. Phys Ther 64:330-336, 1984
89. MacIntyre DL, Robertson DC: Quadriceps muscle activity in women runners with and without patellofemoral pain syndrome. Arch Phys Med Rehabil 73(1):10-14, 1992
90. MacNab I: Recurrent dislocation of the patella. J Bone Joint Surg 34A(4):957-967, 1952
91. Malek MM, Mangine RE: Patellofemoral pain syndromes: A comprehensive and conservative approach. J Orthop Sports Phys Ther 2(3):108-116, 1981
92. Mariani PP, Caruso I: An electromyographic investigation of subluxation of the patella. J Bone Joint Surg 61B(2):169-171, 1979
93. McConnell J: The management of chondromalacia patella. A long-term solution. Aust J Physiother 32:215-223, 1986
94. Merchant AC: Classification of patellofemoral disorders. Arthroscopy 4(4):235-240, 1988
95. Merchant AC, Mercer RL, Jacobsen RH, Cool CR: Roentgenographic analysis of patellofemoral congruence. J Bone Joint Surg 56A(7):1391-1396, 1974
96. Milgrom C, Finestone A, Eldad A, Shamkovitch N: Patellofemoral pain caused by overactivity. A prospective study of risk factors in infantry recruits. J Bone Joint Surg 73A:1041-1043, 1991
97. Milgrom C, Finestone A, Shlamkovitch N, Giladi M, Radin E: Anterior knee pain caused by overactivity. Clin Orthop 331:256-260, 1996
98. Nimon G, Murray D, Sandow M, Goodfellow J: The natural history of anterior knee pain: A 14-to 20-year follow-up of nonoperative management. Orthop Trans 20(1):91, 1996, (abstract)
99. Ogilvie-Harris DJ, Roscoe M: Reflex sympathetic dystrophy of the knee. J Bone Joint Surg 69B(5):804-806, 1987'
100. Palumbo PM Jr: Dynamic patellar brace: A new orthosis in the management of patellofemoral disorders. A preliminary report. Am J Sports Med 9(1):45-49, 1981
101. Patel D: Arthroscopy of the plicaesynovial folds and their significance. Am J Sports Med 6(5):217-225, 1978
102. Paulos L, Rosenberg TD, Drawbert J, Manning J, Abbott P: Infrapatellar contracture syndrome. An unrecognized cause of knee stiffness with patella entrapment and patella inferas. Am J Sports Med 15:331-334, 1987
103. Paulos L, Rusche K, Johnson C, Noyes FR: Patellar malalignment: A treatment rationale. Phys Ther 60(12):1624-1632, 1980
104. Payne R: Neuropathic pain syndrome with special references to causalgia in reflex sympathetic dystrophy. Clin J Pain 2:59-73, 1986
105. Powers CM, Landel R, Perry J: Timing and intensity of vastus muscle activity during functional activities in subjects with and without patellofemoral pain. Phys Ther 76(9):946-955, 1996
106. Powers CM, Maffucci R, Hampton S: Rearfoot posture in subjects with patellofemoral pain. J Orthop Sports Phys Ther 22(4):155-160, 1995
107. Radin EL: A rational approach to the treatment of patellofemoral pain. Clin Orthop 144:107-109, 1979
108. Reynolds L, Levin TA, Medeiros JM, Adler NS, Hallum A: EMG activity of the vastus medialis oblique and the vastus lateralis and their role in patellar alignment. Am J Phys Med 62(2):61-70, 1983
109. Sammarco GJ, Burnstein AH, Frankel VH: Biomechanics of the ankle: A kinematic study. Orthop Clin North Am 4(1):75-96, 1973
110. Sandow MJ, Goodfellow JW: The natural history of anterior knee pain in adolescents. J Bone Joint Surg 67B(1):36-38, 1985
111. Schutzer SF, Ramsby GR, Fulkerson JP: Computed tomographic classification of patellofemoral pain patients. Orthop Clin North Am 17(2):235-248, 1986
112. Shellock FG, Mink JH, Deutsch AL, Molnar T: Effects of a newly designed patellar realignment brace on patellofemoral relationships. Med Sci Sports Exerc 27(4):469-472, 1995
113. Shelton GL, Thigpen LK: Rehabilitation of patellofemoral dysfunction: A review of the literature. J Orthop Sports Phys Ther 14(6):243-249, 1991
114. Simoneau GG, Wilk KE: Electromyographic activity of vastus medialis and lateralis during four exercises. Phys Ther 73(6):580, 1993 (abstract)
115. Siwek CW, Rao JP: Ruptures of the extensor mechanism of the knee joint. J Bone Joint Surg 63A(6):932-937, 1981
116. Snyder-Mackler L, Delitto A, Stralka SW, Bailey SL: Use of electrical stimulation to enhance recovery of quadriceps femoris muscle force production in patients following anterior cruciate ligament reconstruction. Phys Ther 74(10):901-907, 1994
117. Soderberg GL, Averett DH, Diaz GY: Electromyographic (EMG) analysis of selected lower extremity musculature in normal subjects during ambulation with and without a Protonics knee brace. Phys Ther 76(5):488, 1996 (abstract)
118. Soderberg CL, Minor SD, Arnold K, Henry T, Chatterson JK, Poppe DR, Wall C: Electromyographic analysis of knee exercises in healthy subjects and in patients with knee pathologies. Phys Ther 67(11):1691-1696, 1987
119. Souza DR, Gross MT: Comparison of vastus medialis obliquus:vastus lateralis muscle integrated electromyographic ratios between healthy subjects and patients with patellofemoral pain. Phys Ther 71(4):310-316, 1997
120. Stanish WD, Rubinovich RM, Curwin S: Eccentric exercise in chronic tendinitis. Clin Orthop 408:65-68, 1986
121. Stanitski CL: Anterior knee pain syndromes in the adolescent. Instr Course Lect 43:211-220, 1994
122. Steadman JR: Nonoperative measures for patellofemoral problems. Am J Sports Med 7(6):374-375, 1979
123. Thomee R, Renstrom P, Karlsson J, Grimby G: Patellofemoral pain syndrome in young women. I. A clinical analysis of alignment, pain parameter, common symptoms and functional activity level. Scand J Med Sci Sports 5(4):237-244, 1995
124. Thomee R, Renstrom P, Karlsson J, Grimby G: Patellofemoral pain syndrome in young women. II. Muscle function in patients and healthy controls. Scand J Med Sci Sports 5(4):245-251, 1995
125. Tomsich DA, Nitz AJ, Threlkeld AJ, Shapiro R: Patellofemoral alignment: Reliability. J Orthop Sports Phys Ther 23(3):200-208, 1996
126. Tria AJ Jr, Palumbo RC, Alicea JA: Conservative care for patellofemoral pain. Orthop Clin North Am 23(4):545-554, 1992
127. Villar RN: Patellofemoral pain and the infrapatellar brace. Am J Sports Med 13(5):313-315, 1985
128. Voight ML, Wieder DL: Comparative reflex response times of vastus medialis oblique and vastus lateralis in normal subjects and subjects with extensor mechanism dysfunction. Am J Sports Med 19(2):131-137, 1991
129. Warren C, Lehmann JF, Koblanski JN: Elongation of rat tail tendon: The effects of temperature and load. Arch Phys Med Rehabil 52:465-474, 1971
130. Warren C, Lehmann IF, Koblanski JN: Heat and stretch procedures: An evaluation of rat tail tendon. Arch Phys Med Rehabil 57:122-126, 1976
131. Wallace L: Lower Quarter Pain: Mechanical Evaluation and Treatment, pp 101-109. Cleveland, OH: Western Reserve Publishers, 1984
132. Wallace L: Rehabilitation following patellofemoral surgery. In: Davies GJ (ed), Rehabilitation of the Surgical Knee, pp 60-62. Ronkonkoma, NY: Cypress, 1984
133. Whitelaw GP Jr, Rullo DJ, Markowitz HD, Marandola MS, DeWaele MJ: A conservative approach to anterior knee pain. Clin Orthop 246:234-237, 1989
134. Wilk KE, Escamilla RF, Fleisig CS, Barrentine SW, Andrews JR, Boyd ML: A comparison of tibiofemoral joint forces and electromyographic activity during open and closed kinetic chain exercises. Am J Sports Med 24:518-527, 1996
135. Wilk KE, Simoneau GE, McGraw T: The electromyographic activity of the quadriceps femoris vastus medialis/ lateralis ratio during squats, leg press and knee extension exercises. Phys Ther 73(6):S80, 1993 (abstract)
136. Wise HH, Fiebert IM, Kates JL: EMG biofeedback as treatment for patellofemoral pain syndrome. J Orthop Sports Phys Ther 6(2):95-103, 1984
137. Woo SL-Y, Buckwalter JA: Injury and Repair of the Musculoskeletal Soft Tissues, Park Ridge, IL: American Academy of Orthopaedic Surgeons, 1988
138. Wright DG, Desai SM, Henderson WH: Action of the subtalar and ankle joint complex during stance phase of walking. J Bone Joint Surg 46A(2):361-382, 1964
139. Zappala FG, Taffel CB, Scuderi GR: Rehabilitation of patellofemoral joint disorders. Orthop Clin North Am 23:555-566, 1992