Patellofemoral Syndrome

Updated: Jan 30, 2017
  • Author: Patrick J Potter, MD, FRCSC; Chief Editor: Consuelo T Lorenzo, MD  more...
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Overview

Practice Essentials

Patellofemoral syndrome (PFS) is characterized by a group of symptoms that are easily diagnosed and often respond to simple management. The common presentation is knee pain in association with positions of the knee that result in increased or misdirected mechanical forces between the kneecap and femur. [1, 2] Ironically, as simple as its presentation is, lack of consensus on the fundamental factors associated with PFS remains. Accordingly, synonyms for the syndrome go in and out of fashion. No agreement exists on the exact pathophysiology, but significant work is being completed on the extent and direction of the associated forces on the patella, as well as on the tracking and alignment of the patella.

Diagnosis and management

Imaging studies should be considered for unusual presentations and for persons in whom PFS is refractory to conservative management. Computed tomography (CT) scanning and magnetic resonance imaging (MRI) allow for imaging at various angles of flexion. CT scanning with the knee in full extension has been demonstrated to more accurately detect patellar subluxation. Cross-sectional viewing allows more direct visualization of the articulation between the patella and femur.

Arthroscopy helps to confirm the diagnosis of PFS by allowing direct visualization of the cartilage surface. Arthroscopic evaluation also provides assessment of joint structures that may cause symptoms that mimic PFS when they are impaired.

The basic exercise principles for management of PFS are restoring muscle balance within the quadriceps group, improving range of motion, and restricting the offending physical activity.

Ice packs frequently are used to decrease pain and inflammation associated with PFS, especially after completing the exercises. Other modalities that may be useful and commonly are incorporated into physical therapy include electrical stimulation and biofeedback.

Patellar taping techniques are used in patients with PFS to reduce friction on the patella. Many physical therapists are trained in the McConnell method of taping the knee.

Proper footwear also is important for individuals with PFS. The physical therapist can evaluate the patient's biomechanics and recommend proper shoes and orthoses, which in turn can lessen knee pain.

Soft knee braces may also be of benefit to patients with PFS. Bracing involves control of the tracking position of the patella and restriction of full knee flexion.

Surgical intervention for patellofemoral syndrome usually is in the form of arthroscopic evaluation followed by release of the lateral attachments of the patella. Most authors agree that surgical treatment rarely is indicated.

Approaches to medicating symptoms of PFS include administration of analgesic medication and administration of nonsteroidal anti-inflammatory drugs (NSAIDs).

Knee pain secondary to defined degenerative changes may be relieved by injecting the joint with steroid or synthetic hyaluronic acid. Such management of patellofemoral syndrome is rare. Injection may be used when many symptoms result from disruption of the joint surface and when all other reasonable measures have failed.

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Pathophysiology

While theories regarding the pathophysiology of patellofemoral syndrome vary, identification of the resultant forces involved in dynamic and static knee positions has been fundamental to the research on this syndrome. Factors believed to contribute to production of retropatellar pain include impairments affecting the patellofemoral joint interface. Such impairments may be a consequence of an unbalanced muscle pull, malalignment between the joint surfaces, excessive knee valgus (ie, increased Q-angle) resulting in increased lateral forces, and quadriceps contractures causing production of excessive leverage forces on the patellofemoral joint surface. Excessive use of the joint, either in frequency of loading or excessive loading, also contributes to the symptoms.

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Epidemiology

Frequency

United States

Patellofemoral syndrome is common in the United States, especially among physically active persons.

International

Patellofemoral syndrome has an estimated prevalence rate of 20% in student populations.

Mortality/Morbidity

Morbidity associated with patellofemoral syndrome is directly proportional to the activity level of the patient. Curtailing physical activities that place unnecessarily stressful demands upon the patellofemoral articulation may be necessary (preferably while substituting other activities into the exercise program).

Race

No racial predilection has been identified for patellofemoral syndrome.

Sex

Patellofemoral syndrome more frequently affects females than males.

Age

Patellofemoral syndrome occurs most frequently in adolescents and young adults.

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