R.T. Strother, MD, CCFP D. Samoil, MD Patellofemoral Syndrome: Therapeutic Regimen Based on Biomechanics SUMMARY RESUME The clinician needs to rehabilitate the Le clinicien doit baser son traitement du syndrome patient with the patellofemoral syndrome femoro-rotulien sur des notions de biomecanique et d'anatomie. Si nous comprenons la physiologie de la based on biomechanics and anatomy. If we rotule et les forces qui lui sont imposees, nous understand the function of the patella and sommes capables d'eduquer nos patients afin de the forces acting upon it, we can educate maximiser l'observance tout au long du traitement et our patients to ensure their compliance le maintien de bonnes habitudes ulterieurement. through both the treatment phase and future maintenance. (Can Fam Physician 1989; 35:1649-1654.) Key words: patellofemoral syndrome, sports medicine

Dr. Strother is Assistant Professor understanding of patellofemoral dis- years is significantly above the mean of Family Medicine and Chairman of ease before initiating treatment. All (21.6) for all other athletic the Sports Medicine Committee, of these areas should be considered injuries.8'-2 Department of Family Medicine, when developing a practical thera- The frequency of injuries increases University of Calgary. Dr. Strother is peutic regimen. during adolescence, and then remains also physician to Team Canada consistently high throughout early Badminton, Luge, and Volleyball. Dr. Incidence adult life, falling off only after the pa- Samoil is a Family Medicine Resident Patellofemoral pain is common.'-' tient approaches the sixth decade.'2 at the University of Calgary. Requests It occurs most often in young people Patellofemoral syndrome is a fre- for reprints to: Dr. R. Strother, Holy and appears to be related to athletic quent diagnosis that is widely distrib- Cross Hospital Family Medicine activities.6'7 In runners, anterior knee uted through many age groups. Clinic, 2202-2 St. S.W., Calgary, pain accounts for up to 57% of knee Alta. T2S 1S5 problems, representing the most fre- Symptoms quent complaint of this group.38-" The classic manifestation of patel- PATELLOFEMORAL syndrome In his survey of athletic injuries, lofemoral pain is retropatellar pain is a common clinical entity. Exer- Dehaven and Lintner'2 found that the that is aggravated by ascending or de- cise is intimately related to both the knee is the most commonly injured scending grades and prolonged sta- treatment and the development of body part, with patellofemoral pain tionary knee flexion.7 Symptoms usu- patellofemoral pain syndrome. In syndrome accounting for 7.4% of all ally begin insidiously and may persist susceptible individuals, inappropriate injuries in men and 19.6% of all inju- for months, with little progression or exercise may precipitate its develop- ries in women. This translates into change in severity. The dull, aching ment and may delay resolution when 18.1% of knee injuries in men and retropatellar pain may be well local- the patient is already injured. 33.2% of knee injuries in women. Of ized and is commonly bilateral.7 Of- The dynamic interaction of activi- all age groups ranging from 12 to 60 ten pain is precipitated by activity3 or ty, individual skeletal alignment, years old, patellofemoral pain was an increase in training mileage and is muscular strength, and flexibility, the most frequent complaint in the aggravated by ascending and de- and their effects on injury require groups aged 13 to 15 years and 25 to scending grades. The discomfort usu- that the clinician develop a total 40 years. The average age of about 26 ally persists for a time after activity,

CAN. FAM. PHYSICIAN Vol. 35: AUGUST 1989 1649 with some relief obtained through at the centre of dynamic and static men for the same angle of knee rest. Aching commonly returns after controlling forces because therapy is extension.4 It follows that activities sitting, for example, in cars, during based on the concept of balancing that increase knee flexion under load flights, and at movie theatres.7"3 these divergent forces.7'21 predispose the individual to develop Patients with patellofemoral pain Contact areas on the underside of symptomS.4.7'26'27'29,30 may also report a subjective sensa- the patella vary with its position in The rich blood supply of the knee tion of instability, or giving way. A the groove.'7 The concept of varying comes from the anastomosis of five muscular "release" of the quadriceps contact areas and force distribution is major arteries. The patella, femoral has been proposed as an explanation important because pressure distribu- condyle, and tibial condyle have a of this symptom.7 This feeling must tion has been theorized to be a prima- wealthy intra-osseous blood supply. be differentiated from other similar ry contributor to the development of The adjacent soft tissues are well sup- symptoms of intra-articular and me- pain. Many surgical techniques di- plied by the circumpatellar anastomo- niscal lesions. Anterior knee pain is a rected toward relieving patellofemo- sis, a multilayered structure that in- symptom common to many diseases ral pain concentrate on correcting cludes subcutaneous fascia, of the knee joint,1415 which can be theoretically abnormal contact retinaculum, capsule synovium, and categorized by region (Table 1).10,.6 pressures. 1,7,13,18,22-25 Recent studies subchondral bone.3' When taking the history of knee pain, have shown, however, that the patel- The nerve supply to the knee con- the physician should keep in mind the lofemoral contact pressures are re- sists of posterior afferent nerves (in- spectrum of disorders that can affect markably uniform in all knees, cluding the posterior articular nerve the knee and their clinical signifi- whether symptomatic or not.26 At the and the terminal branch of the obtu- cance. least, contact area pressures are of rator nerve), the anterior afferent debatable value in directing therapy. nerves (including branches of the Biomechanics Biomechanically, the patella's femoral nerve to the quadriceps mus- In order to elucidate the various function is far more complex than cles), the common perineal nerve, factors involved in patellofemoral simply increasing the lever arm dur- and the saphenous nerve.32 The deep pain, it is useful to review the anato- ing extension and acting like a fric- fibrous substance of ligaments or my and biomechanics of the patello- tionless pulley. The joint acts as a le- menisci are aneural; however, the femoral articulation. The patella ver mechanism with different forces presence of mechanoreceptors in the functions, first of all, to centralize in the patellar ligament and the qua- joint capsule is well documented.32'33 and guide the forces of the divergent driceps tendon. Moreover, the ratio The synovium and subchondral muscle groups of the quadriceps.7"7 between ligament force and tendon bone have pain fibres.7 Articular car- Secondly, the patella acts to increase force changes as a function of the the effective lever arm of the quadri- knee flexion-extension angle.'8 ceps, providing both flexor and ex- Therefore, the patellofemoral joint Table 1 tensor mechanical advantage.7 7"8 Fi- acts more like a balance beam than a Causes of Anterior Knee Pain nally, the patella provides a pulley.27 This important new concept Patella protective bony shield for both func- calls for a re-evaluation of the angles Patellofemoral pain syndrome tion and cosmesis.'7 of flexion considered most suitable Patellar tendonitis Significant forces act on the patella for rehabilitation during seated knee Fat pad syndrome as it tracks proximally to distally in extension. General synovitis association with increasing knee flex- An understanding of the forces en- Quadriceps tendonitis ion. As it is drawn into the trochlear countered by the patella at varying Subluxing, dislocating patella groove (its articulation with the fe- degrees of flexion is the key to devel- Osgood-Schiatter disease mur), the patella travels a course oping a treatment protocol. Tradi- Prepatellar bursitis forming a gentle "C," open to the tionally it was thought that the patel- Retropatellar tendonitis side. Stability in the first 200 of flex- lofemoral joint contact pressure Medial ion is provided by soft tissues with increased linearly through ever-in- Pes anserinus bursitis support dependent upon muscle creasing joint flexion. New biome- Roschel's bursitis tension. 17"19'20 The muscle tension chanical evidence suggests that force Stress fracture provided by the quadriceps mecha- transmission through the knee joint Lateral nism involves the pull of two diver- may be influenced in a non-linear Bursitis gent forces. The vastus medialis mus- way by the level of the static Popliteus tendonitis cle, located distally and medially, acts preload.21 1liotibial band syndrome to stabilize the patella medially. In any case, the force transmitted Excessive lateral pressure syndrome Counteracting the vastus medialus from patella to femur will increase as Intra-articular muscle, the pull of the vastus lateralis flexion increases. At 900 of flexion, Torn meniscus, meniscal lesions muscle couples with the iliotibial approximately four times the body Ligament tear band. In addition, the forces of the weight is transferred through the pa- Arthritis patellofemoral medial and lateral lig- tellofemoral joint, and at 1200 of flex- Lpose body aments help maintain proper tracking ion, this transfer increases to about Medial synovial plica syndrome of the patella throughout its motion eight times body weight. Women Reflex sympathetic dystrophy along the knee joint.3'7 The clinician have been found to develop higher Osteochondritis dissecans must understand that the patella lies degrees of compressive force than Source: See references 10 and 16. 1650 CAN. FAM. PHYSICIAN Vol. 35: AUGUST 1989 tilage itself has no pain-receptive has generated considerable contro- subpopulation of patients who exhibit nerve endings and presumably causes versy. The accepted measurements a reluctance to have the patella dis- pain indirectly when products of de- vary widely. Normal results are 80 to placed laterally.7'43 Their treatment generating articular cartilage irritate, 100 in men and 14° to 150 in women. must include stabilization procedures swell, and stretch the synovium and Signs of patellofemoral pain can be and exercises.44 capsule.7'34 elicited by compressing the patella Effusion is uncommon in patients Although various explanations of against the underlying trochlear with patellofemoral pain. Swelling in the cause of patellofemoral pain have facets.7'41 This increases the pressure and around the knee joint suggests been suggested, including prolonged in the subchondral bone.7 The patella intra-articular pathology and is likely stress, 7,35 increased pressure from may also be displaced medially or lat- to be a result of trauma or synovial misalignment,3,7,36 chronic strain of erally in an extended relaxed knee irritation.734 Although a cascade hy- peripatellar soft tissues,3'36'37 and arti- and palpated on its medial and lateral pothesis relates patellofemoral pain cular cartilage degeneration with sub- underside for tenderness. Tenderness to irritation of the synovium by carti- sequent irritation,7'35 no general con- over the medial border of the patella lage breakdown products, patello- sensus exists at present (Table 2).58 and the medial retinaculum may re- femoral pain is more likely to be ac- Theoretically, then, patellofemoral veal a subluxation or malalignment companied by effusion in older pain arises from fibres in the synovi- problem.7 patients because the synthesis of new um, subchondral bone, and lateral Muscular control of the patellar matrix is presumed to overcome deg- patellar retinaculum. tracking mechanism is important in radation in young patients.34 To con- Patellofemoral pain and chondro- determining the cause of patellofem- clude the examination, painful and malacia have been shown to be oral pain syndrome and in addressing tender areas should be localized and unrelated. 16'38'39 Chondromalacia rehabilitative exercises. The vastus charted, and warmth, numbness, or means "soft cartilage" and describes medialis muscle may be inadequate hyperesthesia should be noted. Final- the anatomic and histologic changes or underdeveloped in some individu- ly, before patellofemoral pain can be in lesions of articular cartilage.7 Pa- als, insufficiency being typified by a diagnosed, a thorough knee examina- tellofemoral pain has not been shown high insertion. The vastus lateralis tion must be completed to exclude in- to lead to chondromalacia or patello- muscle insertion is equally important tra-articular and meniscal lesions.41 femoral arthritis in later years.7 in that tightness may predispose to Examination excess lateral pressure syndrome.3 Investigations This may be tested for by pushing the The usefulness of radiographs in In sorting through the differential patella medially while palpating the the workup of patellofemoral pain re- diagnoses of knee pain, it is useful to lateral retinacular area for tight mains limited.20 Many authors specify remember a few important points. bands.42 Additional factors that may that plain X-ray films should be taken The examination of the patient who influence patellofemoral alignment with special views and various tan- complains of patellofemoral pain are tight hamstrings and Achilles ten- gential angles.43'45'46 Except for ruling must be thorough. The patient should dons, heel varus, excessive midfoot out other diseases, however, X-ray be undressed to shorts and bare feet pronation with weight bearing, and films are useful only in patients with in order to facilitate visual inspection femoral neck anteversion.6 prolonged problems, previous sur- of posture and stance. Any pelvic An important group of patients are gery, effusions, or instability, or in obliquity, varus or valgus abnormali- those with patellar dislocation or sub- patients older than 40 years of ties, tibial torsion, evidence of hyper- luxation. They represent a distinct 720,29'36.47 pronation, or rigid supination of the age. foot should be noted, measured, and Table 2 documented.29 Biomechanical Contributory Factors for Patellofemoral Pain During inspection of the knee, it is important to look for skin changes, Variation in shape of the patella swelling, quadriceps atrophy, and pa- Patella alta tellar position. Although leg lengths Lateralization of patella should always be measured, clinical Pronation of foot and ankle methods to measure leg length in- Abnormal femoral rotation equality based on palpation of certain Abnormal varus or valgus angle prominent osteal points have proved Abnormal Q angle to be inaccurate, with observer error Increased knee joint laxity of up to 10 mm.40 Muscular imbalance The Q angle should be measured Imbalance between medial and lateral patellofemoral by intersecting a line from the anteri- ligaments and retinacula or superior iliac spine to the midpor- Abnormal flexion of knee joint tion of the patella with a line from the Abnormal femoral rotation pattern during gait tibial tubercle to the midportion of Tibial torsion the patella. Evidence of malalign- Increased sulcus angle ment includes an increased or de- Abnormal articular cartilage or subchondral bone creased Q angle. This measurement Trauma holds some clinical significance, but Source: See references 5 and 8. CAN. FAM. PHYSICIAN Vol. 35: AUGUST 1989 1651 Although they are limited, comput- plished, an appropriate program of have an analgesic and anti-inflamma- ed axial tomographic (CAT) scans stretches, exercises, orthotic devices, tory effect. Chrisman and show promise. A CAT scan helps eval- and education could be applied to colleagues34'54 have shown that ASA uate patellofemoral tracking through minimize the risk of developing inhibits release of cathepsin, an en- the first 300 of flexion.20 In many in- symptoms. We should identify predis- zyme that causes cartilage matrix stances, patellar lateralization and posed individuals and, through ag- breakdown.734M54 Nonsteroidal anti- tilting will not show up on X-ray films gressive preventive measures, help inflammatory drugs (NSAIDS) may because the patella becomes congru- them to avoid dysfunction. Philo- moderate recalcitrant patellofemoral ent after 300 of flexion. The CAT scan sophically, an injury should be pain. Some physicians, however, is most effective for just this sort of looked upon as a treatment failure! have not been impressed with the ef- dynamic evaluation. Ultimately CAT Controlling Inflammation fectiveness of ASA or the NSAIDS.3455 scans identify those for whom surgery Idealism aside and reality applied, Local physical treatments, such as may be unadvisable.35'47 the family physician needs an orga- ultrasound and interfering currents, Arthroscopy is useful to exclude in- nized protocol for patients with patel- have been used with success in our ternal derangement and to document lofemoral pain. In the first phase clinic. These methods control pain by chondromalacia (and wash out the (controlling acute inflammation), the decreasing the sensitivity of pain re- joint).42 About 40% to 60% of pa- principles of modified rest, educa- ceptors. tients have a medial synovial shelf. tion, and anti-inflammatory treat- Braces. Braces are purported to The medial synovial shelf syndrome ment are prescribed. have varied rates of effectiveness."-57 can be identified and treated effec- Modified Rest. Modified rest is Most braces are designed to prevent tively with arthroscopy by excising a lateral subluxation and support the small portion of the shelf.48 In pa- based on the concept that an athlete must maintain cardiorespiratory fit- patella without putting direct pres- tients who have symptoms of exces- sure on it. Success rates ranging from sive lateral pressure syndrome, arth- ness and general muscular strength and endurance while protecting the 64% to 93% have been reported.7'58 roscopic lateral release is easily In one study, 82% improved after six performed.48 affected body part.3 A regimen of modified rest, then, requires a knowl- weeks with a brace and 44% im- Recently, the use of the techneti- proved without a brace, but only 35% um-99m bone scan in evaluating pa- edge of biomechanics and patellofem- oral loading. The athlete will wish to showed improvement after 12 months tients with patellofemoral pain has with a brace.59 Thus, improvement been studied.4950 The bone scan re- remain active, but must be educated about which activities overload the appears to be more limited as time sults showed that 48% of painful progresses. The brace should be con- knees had an increased uptake com- articulation. Primarily, these include any activities in the flexed knee posi- sidered an alternative to immobiliza- pared with 9% for normal joints.50 tion because it minimizes the load on The largest problem with the bone tion, especially weight-bearing exer- cise. This would specify avoidance of the patellofemoral joint and prevents scan is its lack of specificity; slightly atrophy of the quadriceps muscle.58 more than half of the patients with climbing, jumping, squatting, and patellar symptoms will have positive kneeling. Stationary bicycling, sus- Orthotic Devices. In patients with scans. This is presumably because of pended water running, and swimming hyperpronation and patellofemoral an alteration of osseous homeostasis are very useful in this phase. pain, orthotic devices are imperative with increased remodeling activity. Patient education is important. A and usually successful. Patients with Positive scan results, therefore, mere- clear understanding of the problem, these disorders are usually runners ly support the diagnosis without help- the aggravating factors, the principles and benefit from orthotic support ing to direct rehabilitation. of treatment, and your ultimate goals when active.7 For orthotic devices to Magnetic resonance imaging has as a patient-physician team ensures a be successful, the limb must be mea- recently been applied to viewing the better outcome. The conservative sured precisely, the orthotic device interior of the joint. Accurate detec- measures applied necessitate high must be constructed to specifications, tion of hyaline cartilage defects and compliance, which is much easier to and instructions for wearing the de- other joint pathology was found to be achieve in an atmosphere of trust and vice must be followed.60 In any athlet- consistent and reliable,51'52 but fur- confidence. When discussing their ic activity, common sense dictates ad- ther studies are necessary. problems, the patients' expectations equate supportive footwear. should be determined. Although re- Treatment turn to activity can usually be made in Rehabilitation Conservative measures remain the approximately four weeks, symptoms The second phase of therapy, reha- cornerstone of any treatment regi- may return or persist, requiring a bilitation, overlaps with controlling men. We divide our protocol into longer rehabilitative period.16'53 inflammation and, later, prevention. three convenient phases: 1) control- Anti-inflammatory Treatment. Treat- The principles of patellofemoral con- ling acute inflammation, 2) rehabili- ments used in patellofemoral pain in- trol and loading direct most of our tation, and 3) prevention. In an ideal clude ice and ASA. Ice relieves pain therapy. The key to rehabilitation is world, these phases of treatment and inflammation; however, the tran- quadriceps exercise.55 These manoeu- would be reversed. sient relative reduction in blood flow vres are necessary to increase the Through education and applied may cause rebound hyperemia and tone of the musculus vastus medialis biomechanics, we can identify pa- discomfort.2 The cold will help re- and to combat the wasting commonly tients at risk. Once this is accom- duce acute muscle spasm.2 Salicylates found in all patellofemoral 1652 CAN. FAM. PHYSICIAN Vol. 35: AUGUST 1989 disorders.55 Strengthening the quadri- position of upright stance. Avoiding Knee injuries in athletes. Sports Med ceps will presumably decrease any ex- going below 300 to 450 will prevent 1986; 3:447-60. cess force across the patella and will excessive loading of the patellofemo- 9. Nilsson S. Overuse knee injuries in relieve lateral drifting by stabilizing ral joint while isotonically loading the runners. Int J Sports Med 1984; the patella medially. quadriceps mechanism.3 5(suppl): 145-8. Isometric contractions of the qua- 10. Rubin BD, Collins HR. Runner's driceps with the knee in full extension Prevention knee. Physician Sports Med 1980; are followed by progressive resistive The final phase of a treatment regi- 8(6):49-58. exercises. Seventy to 100 isometric men consists of prevention, the key- 11. Gibson J, Davies JE, Crane J, Henry AN. Knee pain in sports people-a pro- contractions can be performed daily stone of which is patient education. If spective study. Br J Sports Med 1987; for a duration of five seconds for each patients understand the nature of 21(3): 115-7. repetition. Straight leg raises lifting their disorder, the fundamentals of 12. DeHaven KE, Lintner DM. Athletic to a 450 angle at the hip are begun patellofemoral loading, and the treat- injuries: comparison by age, sport, and with 10 to 15 repetitions, performed ment goals, recurrences will be limit- gender. Am J Sports Med 1986; at a rate of 20 to 40 daily.255 These ed. Aggressive stretching of ham- 14(3):218-24. straight leg raises will maximally strings, the iliotibial tract, and 13. Fabrin J, Damgaard-Iversen B. Patel- stress the quadriceps muscle without quadriceps should be instituted on a lofemoral pain syndrome treated by ante- compression. daily basis. The principles of warm- rior displacement of the tibial tuberosity patellofemoral Isomet- a.m. Bandi. Acta Orthop Belg 1986; ric exercises are recommended for up and cool-down need to be rein- 52(5):645-50. the hamstrings and upper body. forced. Finally, the exercises institut- 14. Insall J. Current concepts review. Pa- Exercises are also important for ed in the rehabilitative phase should tellar pain. J Bone Joint Surg [Am] 1982; uninjured legs.61 Runners are encour- be incorporated into a maintenance 64:147-52. aged to cycle or swim. Straight leg program. 15. Hejgaard N. La chondromalacie rotu- raises can be performed gradually Most patients with patellofemoral lienne. Un syndrom resultant de differ- with weights, starting with 2 to 3 lbs disease will respond to an organized, entes etioloqies. Acta Orthop Belg 1982; (1 to 1.3 kg) and increasing to 12 to conservative protocol. Conservative 48:486-94. 15 lbs (5.4 to 6.8 kg),2 or even up to treatment is very successful, with re- 16. Fulkerson JP, Schutzer SF. After fail- 20 to 30 lbs (9 to 13.5 kg).55 sponse rates of 82% to 93%. 16.23,35,37,63 ure of conservative treatment for painful At this point, the patient can It is paramount that the physician patellofemoral malalignment: lateral re- lease or realignment? Orthop Clin North resume full activity and a mainte- understand the biomechanics, anato- Am 1986; 17(2):283-8. nance program of quadriceps exer- my, and pathology of this problem in 17. Hungerford DS, Barry M. Biome- cises can be instituted.62'63 The use of order to design a thoughtful and ef- chanics of the patellofemoral joint. Clin eccentric exercises, where muscles fective program. Through the educa- Orthop 1979; (144):9-15 lengthen when they contract, is the tion of our patients, we encourage 18. Eijden TMGJ, Konwenhoven E, latest trend in muscle rehabilitation. compliance with our program, ensur- Weijs WA. The influence of anterior dis- Concentric and eccentric exercise ing better prospects for recovery and placement of the tibial tuberosity on the programs,2 side-to-side leg hops, and future function. U patellofemoral biomechanics. Int Orthop if available, controlled motion and 1987; 11:215-21. variable resistance machines (Cybex 19. Dugdale TW, Barnett PR. Historical or Orthotron) may be helpful.6l With References background: patellofemoral pain in young or without machines, however, the 1. Zarins B, Adams M. Knee injuries in people. Orthop Clin North Am 1986; sports. N Engl J Med 1988; 17(2):211-9. basic principle of exercise is that a 318(15):950-61. muscle becomes stronger when it 20. Schutzer SF, Ramsby GR, Fulkerson 2. Stanitski CL. Rehabilitation following JP. The evaluation of patellofemoral pain works against resistance.1 knee injury. Clin Sports Med 1985; using computerized tomography. Clin A controversy rages over the bene- 4(3):495-511. Orthop 1986; (204):286-93. fits versus the risks of seated knee ex- 3. Taunton JE, Clement DB, Smart GW, 21. Hvid I. The stability of the human pa- tensions. Even in the short arc, no McNicol KL. Non-surgical management tellofemoral joint. Eng Med 1983; 12:55. more than 300 of knee flexion, these of overuse knee injuries in runners. Can J 22. Hejgaard N, Arnoldi CC. Osteomy of exercises may be detrimental.55 The Sport Sci 1987; 12:11-8. the patella in the patellofemoral pain syn- reason for doing short arc knee ex- 4. Nisell R, Ekholm J. Patellar forces drome. Int Orthop 1984; 8:189-94. tension was the false concept that the during knee extension. Scand J Rehab 23. Micheli LJ, Stanitski CL. Lateral pa- patella was under less load in this po- Med 1955; 17:63-74. tellar retinacular release. Am J Sports sition or was out of the articulation 5. Fairbank JCT, Pynsent PB, vanPo- Med 1981; 9:330. with the trochlear facets. Static equa- ortvliet JA, Phillips H. Mechanical factors 24. Krompinger WJ, Fulkerson JP. Lat- tions indicate that the patella may ac- in the incidence of knee pain in adoles- eral retinacular release for intractable lat- cents and young adults. J Bone Joint Surg eral retinacular pain. Clin Orthop 1983; tually be under maximum load at this [Br] 1984; 66-B(5):685-93. 179:191-3. terminal portion of knee extension, 6. Yates C, Grana WA. Patellofemoral and it does not matter whether or not 25. Bessette GC, Hunter RE. The Ma- pain-a prospective study. Orthopedics quet procedure. Clin Orthop 1988; it is in the trochlear groove. 1936; 9(5):663-7. (232):159-67. to A more sensible approach is 7. Cox JS. Patellofemoral problems in 26. Hille B, Schulitz K-P, Henrichs C, have the patient do squats to no more runners. Clin Sports Med 1985; Schneider T. Pressure and contact-surface than 300. Squats axially load the pa- 4(4):699-715. measurements within the femoropatellar tella and knee joint in the physiologic 8. Kujala UM, Kvist M, Osterman K. joint and their variations following lateral CAN. FAM. PHYSICIAN Vol.35: AUGUST 1989 1653 release. Arch Orthop Trauma Surg 1985; femoral mnalalignment. Clin Orthop 1987; and intraarticular pathology. Am J Sports 104:275-82. (215):243-7. Med 1987; 15(5):455-63. 27. Buff HN, Jones LC, Hungerford DS. 40. Kujala UM, Friberg 0, Aalto J, Kvist 52. Yulish BS, Montanez J, Goodfellow Experimental determination of forces M, Osterman K. Lower limb asymmetry DB, Bryan PJ, Mulopulos GP, Modic transmitted through the patellofemoral and patellofemoral joint incongruence in HT. Chondromalacia patellaea: assess- joint. J Biomech 1988; 21(1):17-23. the etiology of knee exertion injuries in ment with MR imaging. Radiology 1987; athletes. Int J Sports Med 1987; 164(2):763-6. 28. Jans HWJ, Dortmans UJMG, Sauren 8(3):214-20. AAHJ, Huson A. An experimental ap- 53. MA. The proach to evaluate the dynamic behavior 41. Sternbach GL. Evaluation of the Gruber conservative treat- of the human knee. J Biomech Eng 1988; knee. J Emerg Med 1986; 4:133-43. ment of chondromalacia patella. Orthop 110(Feb):169-73. Clin North Am 1979; 10:105-15. 42. Larson RL, Cabaud HE, Slocum DB, 29. Lutter LD. The knee and running. James SL, Keenan T, Hutchinson T. The 54. Chrisman OD, Snook GA, Wilson Clin Sports Med 1985; 4(4):685-97. TC. The protective effect of aspirin patellar compression syndrome: surgical against degradation of human articular 30. Huberti HH, Hayes WC. Patellofem- treatment by lateral retinacular release. cartilage. Clin Orthop 1972; 84:193-6. oral contact pressures. J Bone Joint Surg Clin Orthop 1978; (134):158-67. [Am] 1984; 66-A(5):715-24. 43. Zenman SC. Acute knee injury. 55. Fisher RL. Conservative treatment of Postgrad Med 1984; 76(8):38-46. patellofemoral pain. Orthop Clin North 31. Sun-Shik Shim, Leung G. Blood sup- Am 1986; 17(2):269-72. ply of the knee joint: a microangiographic 44. Hawkins RJ, Bell RH, Anisette G. study in children and adults. Clin Orthop Acute patellar dislocations. Am J Sports 56. Millet C, Drez D. Knee braces. 1986; (208):119-25. Med 1986; 14(2):117-20. Orthopaedics 1987; 10(12):1777-80. 32. Kennedy JC, Alexander IJ, Hayes 45. Laurin CA, Dussault R, Levesque 57. France EP, Paulos LE, Jayaraman G, KC. Nerve supply of the human knee and HP. The tangential X-ray investigation of Rosenberg TD. The biomechanics of lat- its functional importance. Am J Sports the pateliofemoral joint. Clin Orthop eral knee bracing. Am J Sports Med 1987; Med 1982; 10(6):329-35. 1979; (144):16-26. 15(5):430-8. 33. Gronblad M, Korkala 0, Liesi P, 46. Perrild C, Hejgaard N, Rosenklint A. 58. Chapman AE. The mechanical prop- Karahariu E. Innervation of synovial Chondromalacia patella. A radiographic erties of human muscle. Exerc Sport Sci membrane and meniscus. Acta Orthop study of the femoropatellar joint. Acta Rev 1985; 13:443-501. Scand 1985; 56:484-6. Orthop Scand 1982; 53:131-4. 34. Chrisman OD. The role of articular 59. Moller BN, Krebs B. Dynamic knee 47. Schutzer SF, Ramsby GR, Fulkerson brace in the treatment of patellofemoral cartilage in patellofemoral pain. Orthop JP. Computed tomographic classification Clin North Am 1986; 17(2):231-4. disorders. Arch Orthop Trauma Surg of patellofemoral pain patients. Orthop 1986; 104:377-9. 35. Steiner HE, Grana WA. The young Clin North Am 1986; 17(2):23547. athlete's knee: recent advances. Clin 48. Dandy DJ. Arthroscopy in the treat- 60. McKenzie DC, Clement DB, Taun- Sports Med 1988; 7(3):527-43. ton JE. Running shoes, orthotics, and in- ment of young patients with anterior knee Med 2:334-7. 36. Insall J. Chondromalacia patellae; pa- pain. Orthop Clin North Am 1986; juries. Sports 1985; tellar malalignment syndrome. Orthop 17(2):221-9. 61. Montgomery JB, Steadman JR. Re- Clin North Am 1979; 10:117. 49. Dye SF, Boll DA. Radionuclide im- habilitation of the injured knee. Clin 37. Fulkerson JP. The etiology of patello- aging of the patellofemoral joint in young Sports Med 1985; 4(2):333-43. femoral pain in young, active patients. adults with anterior knee pain. Orthop 62. DeHaven KE, Dolan WA, Mayer PJ. Clin Orthop 1983; 179:129-33. Clin North Am 1986; 17(2):249-62. Chondromalacia patellae in athletes- 38. Stougard J. Chondromalacia of the 50. Hejgaard N, Diemer H. Bone scan in clinical presentation and conservative patella-physical signs in relation to oper- the patellofemoral pain syndrome. Int management. Am J Sports Med 1979; ative findings. Acta Orthop Scand 1975; Orthop 1987; 11:29-33. 7:5-11. 46:685-94. 51. Wojtys E, Wilson M, Buckwalter K, 63.DeHaven KE, Dolan WA, Mayer PJ. 39. Sojbjerg JO, Lauritzen J, Hvid I, Boe Braunstein E, Martel W. Magnetic reso- Chondromalacia patellae and the painful S. Arthroscopic determination of patello- nance imaging of knee hyaline cartilage knee. Am Family Physician 1980; 21:117.

1654 CAN. FAM. PHYSICIAN Vol. 35: AUGUST 1989