AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

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. 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 the tracking and alignment of the patella.

Pathophysiology

While theories regarding the pathophysiology of PFS 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.

Frequency

United States

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

International

A prevalence rate of 20% has been estimated in student populations.

Mortality/Morbidity

Morbidity associated with PFS 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 this condition.

Sex

PFS more frequently affects females than males.

Age

PFS occurs most frequently in adolescents and young adults.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

• Knee pain is the most common presentation of PFS.
• • The pain characteristically is located behind the kneecap (ie, retropatellar) and most often manifests during activities that require knee flexion and forceful contraction of the quadriceps (eg, during squats, ascending/descending stairs).
  • Pain may worsen in intensity, duration, and rapidity of onset if the aggravating activity is performed repeatedly.
  • Pain may be exacerbated by sitting with the knee flexed for a protracted period of time, such as while watching a movie, hence leading to the terms "theatre sign" and "movie-goer's knee." Patients with this condition often may prefer to sit at an aisle seat, where they may more frequently keep the knee extended.
• Symptoms often occur during the activity, such as playing volleyball for 30 minutes, or may occur later after the activity has been completed.
• Sometimes symptoms manifest as late as the next day.

Physical

Physical examination should include examination of the musculoskeletal system, including the following:

• The upper and lower body should be examined to exclude generalized diseases that make up the differential diagnoses (eg, osteoarthritis).
• The usual physical findings are localized around the knee.
• Tenderness often is present along the facets of the patella. The facets are most accessible to palpation by manipulation of the patella while the knee is fully extended and the quadriceps muscle is relaxed. Manual positioning of the patella medially, laterally, superiorly, and inferiorly allows for palpation of the respective facets.
• An apprehension sign may be elicited by manually fixing the position of the patella against the femur and having the patient contract the ipsilateral quadriceps.
• Crepitus may be present, but, if present in isolation, crepitus does not allow for definitive diagnosis.
• Determine the Q-angle by measuring the angle between the tibia and femur. Use the attachment of the patella to the patellar tendon as the intersection point.
• Examination of gait may demonstrate excessive foot pronation, excessive knee valgus, or an antalgic gait pattern.
• Repetitive squatting may reproduce knee pain.
• Use the physical examination and historical details to help exclude other diagnoses.
• Examination of the contralateral limb is equally important, as the syndrome often is bilateral. However, one side usually manifests more symptoms.
• Palpation of the tibial tuberosity may detect tenderness suggesting that other impairments also are present.
• Determining the bulk of the vastus medialis is possible because of its superficial position with little overlying tissue. Bulk may be observed by direct visualization during contraction. The vastus medialis is believed to be the most active muscle in the last 15° of resisted knee extension, making this the best arc of movement for assessing its strength.
• Genu recurvatum and hamstring weakness may contribute to the occurrence of PFS, and, therefore, identifying such impairments may aid in the choice of management.

Causes

The potential causes of PFS remain controversial and, therefore, are termed more appropriately as associated factors. Overuse, overloading, and misuse of the patellofemoral joint seem to be the cornerstone factors on which most authors agree.

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Referred pain from hip
Osgood-Schlatter syndrome
Larsen disease
Patellofemoral arthritis
Neuroma
Patellar tendonitis
Plica syndromes of the anterior knee
Radicular pain
Infection of the knee joint
Tumor (eg, knee joint, femur)

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• Laboratory studies generally are not indicated for the diagnosis of PFS.

Imaging Studies

• Imaging studies usually are not necessary for the physician to make the diagnosis or to recommend treatment. Imaging studies should be considered for unusual presentations and for persons in whom the syndrome is refractory to conservative management.
• • Skyline views should be included with anterior-posterior (AP) and lateral radiographic imaging of the knee. Limited positions of flexion are available for such viewing. These radiographs provide more of an indirect observation of what is happening within the articulation.
  • Lateral patellar tilt and a high riding patella (patella alta) may be observed.
  • Osteophytes or joint space narrowing may be identified, suggesting arthritic changes in the articular cartilage.
• Nuclear scans are less likely to be of value in defining PFS and are more useful in helping identify other less common conditions that may mimic PFS, as outlined in the differential diagnoses. When changes have occurred in the retropatellar cartilage, mild increases in uptake of radionucleotide may be observed. Increased uptake of radionucleotide is not limited to the patella; it may be seen in the proximal tibia, distal femur, or patella.
• CT scan and MRI
• • CT scan and MRI allow for imaging at various angles of flexion.
  • CT scan 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.
  • Schutzer et al identified 3 patterns of malalignment using CT imaging:
    • Type 1 includes patellar subluxation without tilt.
    • Type 2 is described as patellar subluxation with tilt.
    • Type 3 is patellar tilt without subluxation.

Other Tests

• Serology, joint aspiration, and related tests are indicated only when alternative diagnoses are suspected. Such investigations are not likely to provide useful information in this syndrome, as it is not a disease entity but rather a group of symptoms occurring sometimes in association with multiple factors, both intrinsic and extrinsic.

Procedures

• Arthroscopy
• • Arthroscopy helps confirm the diagnosis by allowing direct visualization of the cartilage surface. Arthroscopic evaluation also provides assessment of the other joint structures that may cause symptoms that mimic PFS when they are impaired.
  • Arthroscopy also has the ability to facilitate surgical alteration of patellar tracking (eg, lateral release). Visualization of the patella may allow for some revision of the cartilage surface. However, most authors agree that surgical treatment is rarely indicated.

Histologic Findings

Histologic findings are dependent upon the extent to which the cartilage surfaces have been compromised. Shearing stresses may result in changes in subchondral bone and dysplasia of the cartilage surface. More severe cartridge changes have been identified in persons with PFS that has been refractory to conservative measures.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Rehabilitation Program

Physical Therapy

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. Quadriceps strengthening traditionally is performed while the knee is flexed 0-30°. Controversy remains as to the extent that the individual muscle groups comprising the quadriceps can selectively be strengthened. Usually, the lateral forces of the vastus lateralis need to be countered better by the vastus medialis. This goal is accomplished best by strengthening all of the quadriceps.

Stretching of the quadriceps should be of long duration (20-30 seconds) and with low force. This technique allows for overcoming neural and connective tissue barriers to lengthening. Exercises to stretch the iliotibial band, hip, hamstring, and calf also are important for patients with PFS. Manual stretching of the lateral retinaculum may be used as a conservative approach, partially mimicking the effect of lateral retinacular release. Physical therapists should educate patients about home exercise programs that include both stretching and strengthening exercises. Ice packs frequently are used to decrease pain and inflammation associated with this condition, 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 the friction on the patella. Many physical therapists are trained in the McConnell method for taping of the knee. Some patients report reduction of pain when wearing the tape. Some individuals report that the taping allows them to complete more functional quadriceps-strengthening activities without anterior knee pain. If successful, the physician or physical therapist can teach the patient self-taping techniques to use at home.

Proper footwear also is important for individuals with PFS. The physical therapist can evaluate the patient's biomechanics and recommend proper shoes and orthotics, which, in turn, can lessen knee pain. Foot orthotics are often of benefit in returning the subtalar joint to a nearly neutral position, thereby reducing foot pronation, which, in turn, reduces rotational forces in the tibia that affect tracking of the patella during locomotion. Improvement in quality of life measures has been demonstrated following provision of custom orthotics to individuals with PFS and excessive foot pronation.

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. Braces vary in the manner in which the patella is restricted (eg, patellar window, patellar bar, patellar horseshoe), but they accomplish the same theoretical result. Braces that are tightly applied directly over the patella should be avoided as they actually increase patellofemoral pressures and may exacerbate the condition.

Occupational Therapy

Recommend a change in activity level or the ergonomics of the offending activity until the symptoms are under control. Activities that require repetitive squatting are a good example. The task or sport may need to be modified to reduce the frequency of squatting, or the patient may need to choose an alternate occupation or recreational activity. Occupational therapists can be of assistance when reviewing the ergonomics of the environment in which symptoms occur with individual patients.

Recreational Therapy

Introducing alternative recreational pursuits and means of fitness may be of benefit in alleviating symptoms when conservative measures are not effective. Modifications in recreational pursuits may need to be only temporary measures if other conservative measures are effective.

Medical Issues/Complications

Most symptoms of PFS resolve with simple measures. As with many exercise routines, patients often fail to adhere to the exercise prescription, resulting in apparent refractory treatment results when the therapeutic approach has not been given a fair trial. Follow-up studies suggest that more than 95% of persons who are compliant with treatment have acceptable or better results.

Surgical Intervention

Surgical intervention 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. Arthroscopy has been cited as assisting the physician with clinical diagnoses; however, the visualization procedure, in and of itself, does not significantly help the symptoms of patellofemoral pain.

• Surgical procedures performed for patellofemoral arthritis include lateral facetectomy and patellar resurfacing.
• Follow-up evaluations long after anterior advancement of the tibial tuberosity suggest limited results with this procedure.
• Research on cartilage transplantation is being performed. Additional surgical options may be added in the future.
• Arthroscopic drilling of osteochondral defects allows healing of the defect with fibrocartilage. This procedure routinely is performed. This form of cartilage is not of the normal type but provides for an improved surface compared to an osteochondral defect.

Consultations

Management of PFS overlaps many specialties. When necessary, consider consultation to answer specific questions regarding refractory response to treatment or optimization of treatment approaches.

Other Treatment

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

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Two approaches for medicating symptoms of PFS are recognized. These approaches are administration of analgesic medication and administration of nonsteroidal anti-inflammatory drugs (NSAIDs). Analgesics commonly are restricted to acetaminophen or aspirin. The choices of NSAIDs available for management of joint pain are expanding continuously. Consider tolerance of medication (which may result in epigastric distress), prior history of gastric ulceration, renal disease, possible interaction with other medications, and cost. The NSAIDs all have similar efficacy, but recent changes in formulation have been made to reduce frequency of adverse effects. Selective COX-2 inhibitors have fewer gastrointestinal adverse effects.

Drug Category: Nonsteroidal anti-inflammatory drugs

No NSAID has been found to be more effective in treating symptoms of PFS than any other, although tolerances of NSAIDs vary between individuals. Listed below are the commonly used NSAIDs. These NSAIDs are used predominantly in the adult population. Except for the COX-2 NSAIDs, most have similar profiles of adverse effects, and most have the same effect on prostaglandins.

Drug Category: Cyclo-oxygenase-2 (COX-2) inhibitors

Although increased cost can be a negative factor, the incidence of costly and potentially fatal GI bleeds is clearly less with COX-2 inhibitors than with traditional NSAIDs. Ongoing analysis of cost avoidance of GI bleeds will further define the populations that will find COX-2 inhibitors the most beneficial.

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Further Inpatient Care

• The standard procedure of treatment for individuals with PFS is performed on an outpatient basis. Inpatient care generally is not indicated.

Further Outpatient Care

• Allow time for conservative measures (eg, exercise) to have a therapeutic effect. A period of 4-6 weeks usually is adequate for some resolution of symptoms. Longer delays before follow-up often result in reduced compliance with treatment recommendations. Reinforcement of treatment goals and strategies is important.

In/Out Patient Meds

• Outpatient medications include common analgesics or NSAIDs (see Medication). Most individuals manage without medication once initial symptoms have been controlled.

Deterrence

• Prevention is accomplished by following exercise recommendations and making changes in activity, as described in previous sections. In female athletes, decreased hamstring-to-quadriceps strength ratios have been associated with an increased prevalence of overuse injuries, suggesting that maintaining adequate hamstring strength may act as a preventative strategy. Braces have been tried on asymptomatic subjects undergoing rigorous basic military training, with a subsequent decrease in the incidence of PFS compared with the subject population that did not use the braces.

Complications

• Complications may result secondary to the effects of NSAID use. Occasional dermatologic reactions occur due to the brace material. Prescribed exercises rarely result in aggravation of symptoms. If a specific activity is determined to be associated with aggravation of symptoms, then accordingly modify the frequency, duration, and intensity of the activity

Prognosis

• The prognosis for full functional recovery is very good. In general, this syndrome is successfully treated with conservative measures. Because the prognosis is so good, refractory cases should be closely reviewed with regard to compliance and understanding of treatment recommendations.

Patient Education

• Educate the patient so that he/she understands which activities aggravate the condition. Also emphasize the need for extended adherence to the exercise regimen. The patient's physical therapist should educate the patient about a home exercise program, making sure the patient has a good understanding of the exercises.
• For excellent patient education resources, visit eMedicine's Foot, Ankle, Knee, and Hip Center, Arthritis Center, and Bone Health Center. Also, see eMedicine's patient education article Knee Pain.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• The most common medical/legal aspects related to PFS are defining the nature of the syndrome, its effect on usual activities, and the prognosis in cases in which onset has occurred as a result of trauma (eg, a work-related injury, automobile-related injury). More specifically, cases in which a direct blow has resulted in an impairment of the cartilage surface may not respond in the same manner as tracking problems. Contusion secondary to dashboard contact, termed dashboard knee, remains a common cause of ongoing knee pain after trauma resulting from a motor vehicle accident.

Special Concerns

• The primary significant concern associated with PFS is that the patient remains active and continues to interact with peers. This goal can be accomplished by making sure the affected youth understands the aggravating and alleviating factors associated with participation in sports and other physical activities. If some athletic activities must be curtailed, ideally there should be an attempt to engage the patient in alternative activities to maintain conditioning (eg, swimming). Long-term goal should include resuming the patient's preferred activities when this is feasible.

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

• Crossley K, Bennell K, Green S, McConnell J. A systematic review of physical interventions for patellofemoral pain syndrome. Clin J Sport Med. Apr 2001;11(2):103-10. [Medline].
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• Handelberg F, Shahabpour M, Van Betten F, et al. CT arthrography and MRI of the patella. Acta Orthop Belg. 1989;55(3):331-8. [Medline].
• Haut RC, Ide TM, De Camp CE. Mechanical responses of the rabbit patello-femoral joint to blunt impact. J Biomech Eng. Nov 1995;117(4):402-8. [Medline].
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• Karlsson J, Thomee R, Sward L. Eleven year follow-up of patello-femoral pain syndrome. Clin J Sport Med. Jan 1996;6(1):22-6.
• Karlsson J, Sward L, Lansinger O. Bad results after anterior advancement of the tibial tubercle for patello-femoral pain syndrome. Arch Orthop Trauma Surg. 1992;111(4):195-7. [Medline].
• Kettunen JA, Visuri T, Harilainen A, et al. Primary cartilage lesions and outcome among subjects with patellofemoral pain syndrome. Knee Surg Sports Traumatol Arthrosc. Mar 2005;13(2):131-4.
• Kujala UM, Friberg O, Aalto T, et al. Lower limb asymmetry and patellofemoral joint incongruence in the etiology of knee exertion injuries in athletes. Int J Sports Med. Jun 1987;8(3):214-20. [Medline].
• Martens M, De Rycke J. Facetectomy of the patella in patellofemoral osteoarthritis. Acta Orthop Belg. 1990;56(3-4):563-7. [Medline].
• Näslund JE, Odenbring S, Näslund UB, Lundeberg T. Diffusely increased bone scintigraphic uptake in patellofemoral pain syndrome. Br J Sports Med. Mar 2005;39(3):162-5.
• Schutzer SF, Ramsby GR, Fulkerson JP. Computed tomographic classification of patellofemoral pain patients. Orthop Clin North Am. Apr 1986;17(2):235-48. [Medline].
• Scott SH, Winter DA. Internal forces of chronic running injury sites. Med Sci Sports Exerc. Jun 1990;22(3):357-69. [Medline].
• Thomee R, Augustsson J, Karlsson J. Patellofemoral pain syndrome: a review of current issues. Sports Med. Oct 1999;28(4):245-62. [Medline].
• Wagenhauser FJ. [Clinical aspects of arthroses]. Verh Dtsch Ges Inn Med. 1989;95:449-62. [Medline].

Article Last Updated: Mar 16, 2006