Background
Patellofemoral joint complaints are one of the most common musculoskeletal complaints in all age groups. Complaints vary from anterior knee pain to peripatellar knee pain to retropatellar knee pain.[1, 2, 3, 4, 5, 6, 7] Nonspecific complaints may include global or generalized knee pain, joint line pain, or posterior knee pain. Often, there is a paucity of objective findings despite subjective complaints. The problem may vary from one of short duration to one of a recurrent or chronic nature.
The etiology of patellofemoral joint syndrome is multifactorial and results from a combination of intrinsic and extrinsic factors.[1, 2, 3, 4, 5, 6, 7] Treatment is often conservative in nature. Because of the variable nature of the complaints and an often lack of objective identifiable pathologic cause of patellofemoral joint complaints, this condition can be difficult to evaluate, diagnose, and treat, which may cause great frustration for the physician and patient alike.[5]
For excellent patient education resources, visit eMedicine's Foot, Ankle, Knee, and Hip Center; Breaks, Fractures, and Dislocations Center; Arthritis Center; and Osteoporosis and Bone Health Center. Also, see eMedicine's patient education articles Knee Pain Overview and Knee Injury.
Related eMedicine topics:
Epidemiology
Frequency
United States
Patellofemoral joint syndrome may affect as many as 25% of all athletes.
Functional Anatomy
The patellofemoral joint is composed of the articulation of the patella with the femoral condyles of the femur. The patella has a configuration of a triangle with its apex directed inferiorly. Superiorly, it articulates with the trochlea, the distal articulating surface of the femur.
The patella is the largest sesamoid bone in the body and protects the knee from direct trauma. Localized within the quadriceps tendon, the patella also acts as a fulcrum for extension of the quadriceps.
Medial movement of the patella is controlled by the vastus medialis oblique (VMO) muscle. Lateral tracking is guided by both the vastus lateralis and the iliotibial band. Patellar motion is further constrained by the patellofemoral ligament, the patellotibial ligament, and the retinaculum.
The patella is engaged with the trochlea at 20-30 º of knee flexion. At 90 º, the patella contacts the lateral and medial femoral facets within the condylar fossa. At 130-135 º of knee flexion, the medial facets of the patella contact the articulating surface of the femoral condyles. In knee extension, the patella abuts the suprapatellar fat pad.
Sport-Specific Biomechanics
The patella lies within the quadriceps tendon and thereby increases the mechanical advantage of the quadriceps mechanism. Not only does the patella increase the force of knee extension by 50%, but it also provides stability to the patellar tendon and minimizes the forces placed on the femoral condyles.
Tracking of the patella begins with the lower patellar border lying in contact with the suprapatellar fat pad when the knee is fully extended. With knee flexion, the patella moves proximally with a lateral shift, which is limited in excursion by the lateral retinaculum. As the knee continues to flex, the tibia internally rotates and the patella moves upward. The amount of force placed on the patellofemoral joint increases with increasing knee flexion. On the other hand, knee hyperflexion increases patellofemoral stress, as does extreme extension.
The vector force placed on the patella may be affected by the Q-angle. The Q-angle is a line created from the anterior superior iliac spine (ASIS) to the mid patella, which intersects with a line from the mid patella to the tibial tubercle when the knee is in full extension. An average Q-angle for a male is 14 º, whereas that for a female is 17 º. Q-angles larger than average can indicate abnormal patellar tracking.
Other factors that may affect the vector force on the patella include the following:
- Femoral anteversion
- Tibial torsion
- Hyperpronation of the foot
- Atrophy of the VMO muscle
- A tight lateral retinaculum
- Patella position (patella alta/baja or subluxation)
- Inflexibility of the quadriceps, hamstring, iliotibial, and calf muscle-tendon units
- General ligamentous laxity
Wieting JM, McKeag DB. Anterior knee pain and overuse. In: Sallis RE, Massimino F, eds. ACSM's Essentials of Sports Medicine. St. Louis, Mo: Mosby-Year Book; 1997:421-32.
Scuderi GR, ed. The Patella. New York, NY: Springer-Verlag; 1995:xii-351.
Wertheimer C. Patellofemoral mechanics as a cause of anterior knee pain. Your Patient and Fitness. 1995;9:19-23.
Eilert RE. Adolescent anterior knee pain. Pediatric Orthopedics. Philadelphia, Pa: Lippincott-Raven; 1991:499-515.
Ruffin MT 5th, Kiningham RB. Anterior knee pain: the challenge of patellofemoral syndrome. Am Fam Physician. Jan 1993;47(1):185-94. [Medline].
Pizzutillo PD. Osteochondroses. In: Sullivan JA, Grana WA, eds. The Pediatric Athlete. Park Ridge, Ill: American Academy of Orthopaedic Surgeons; 1990:224.
Walsh WM. Knee injuries. In: Mellion MB, Walsh WM, Shelton GL, eds. The Team Physician's Handbook. Philadelphia, Pa: Hanley & Belfus; 1990:414-39.
Hudson Z, Darthuy E. Iliotibial band tightness and patellofemoral pain syndrome: a case-control study. Man Ther. Feb 28 2008;epub ahead of print. [Medline].
Dixit S, DiFiori JP, Burton M, Mines B. Management of patellofemoral pain syndrome. Am Fam Physician. Jan 15 2007;75(2):194-202. [Medline].
Cowan SM, Bennell KL, Hodges PW. Therapeutic patellar taping changes the timing of vasti muscle activation in people with patellofemoral pain syndrome. Clin J Sport Med. Nov 2002;12(6):339-47. [Medline].
Balachandar V, Barton C, Morrissey D. The efficacy of patellar taping in individuals with patellofemoral pain syndrome: a systematic review. Br J Sports Med. Dec 2011;45(15):A18. [Medline].
[Best Evidence] Syme G, Rowe P, Martin D, Daly G. Disability in patients with chronic patellofemoral pain syndrome: a randomised controlled trial of VMO selective training versus general quadriceps strengthening. Man Ther. Jun 2009;14(3):252-63. [Medline].
Earl JE, Vetter CS. Patellofemoral pain. Phys Med Rehabil Clin N Am. Aug 2007;18(3):439-58, viii. [Medline].
LaBotz M. Patellofemoral syndrome: diagnostic pointers and individualized treatment. Phys Sportsmed. July 2004;32(7):22-9. [Full Text].
Weil EK. Pain and pyrexia. Residents' Edition Prescribing Reference. 5th ed. New York, NY: Prescribing Reference, Inc; 1996:164-8.
Kelly GS. The role of glucosamine sulfate and chondroitin sulfates in the treatment of degenerative joint disease. Altern Med Rev. Feb 1998;3(1):27-39. [Medline]. [Full Text].
Ott B, Cosby NL, Grindstaff TL, Hart JM. Hip and knee muscle function following aerobic exercise in individuals with patellofemoral pain syndrome. J Electromyogr Kinesiol. Aug 2011;21(4):631-7. [Medline].
Ferber R, Kendall KD, Farr L. Changes in knee biomechanics after a hip-abductor strengthening protocol for runners with patellofemoral pain syndrome. J Athl Train. Mar-Apr 2011;46(2):142-9. [Medline]. [Full Text].
Freeman AJ, Jacobson NA, Fogg QA. Anatomical variations of the plantaris muscle and a potential role in patellofemoral pain syndrome. Clin Anat. Mar 2008;21(2):178-81. [Medline].
Liebensteiner MC, Szubski C, Raschner C, et al. Frontal plane leg alignment and muscular activity during maximum eccentric contractions in individuals with and without patellofemoral pain syndrome. Knee. Feb 21 2008;epub ahead of print. [Medline].
Vicenzino B, Collins N, Crossley K, et al. Foot orthoses and physiotherapy in the treatment of patellofemoral pain syndrome: a randomised clinical trial. BMC Musculoskelet Disord. Feb 27 2008;9(1):27. [Medline]. [Full Text].
Print
