eMedicine Specialties > Physical Medicine and Rehabilitation > Lower Limb Musculoskeletal Conditions

Patellofemoral Syndrome

Patrick J Potter, BSc, MD, FRCP(C), Associate Professor, Physical Medicine and Rehabilitation, The University of Western Ontario; Consulting Staff, Department of Physical Medicine and Rehabilitation, St Joseph's Health Care Centre
Keith AJ Sequeira, MD, Associate Director of Spinal Cord Medicine, Assistant Professor, Department of Physical Medicine and Rehabilitation, Parkwood Hospital, University of Western Ontario

Updated: Jul 15, 2009

Introduction

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.¹ 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.

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.

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.

Clinical

History

Knee pain is the most common presentation of patellofemoral syndrome.
- 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 of a patient with patellofemoral syndrome should include examination of the musculoskeletal system, including the following²:

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 it is situated superficially and has 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 patellofemoral syndrome remain controversial and are therefore more appropriately referred to as associated factors.¹ Overuse, overloading, and misuse of the patellofemoral joint seem to be the cornerstone factors on which most authors agree.

Differential Diagnoses

Patellofemoral Arthritis
Prepatellar Bursitis

Workup

Laboratory Studies

Laboratory studies generally are not indicated for the diagnosis of patellofemoral syndrome.

Imaging Studies

Imaging studies usually are not necessary in order for a physician to diagnose or recommend treatment for patellofemoral syndrome (PFS). 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.³
Nuclear scans are less likely to be of value in defining PFS and are more useful in helping to 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.⁴
Computed tomography (CT) scanning and magnetic resonance imaging (MRI)
- CT scanning and 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.
- Schutzer et al identified 3 patterns of malalignment using CT scanning⁵:
  - 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 (intrinsic and extrinsic).⁶

Procedures

Arthroscopy
- Arthroscopy helps to confirm the diagnosis patellofemoral syndrome (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.
- 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 on 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 cartilage changes have been identified in persons with patellofemoral syndrome that has been refractory to conservative measures.

Treatment

Rehabilitation Program

Physical Therapy

The basic exercise principles for management of patellofemoral syndrome (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 regarding the extent to which the individual muscle groups making up 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 performed 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 stretching and strengthening exercises.

Syme et al found that selective and general physical therapy are valuable for the rehabilitation of patients with patellofemoral syndrome (PFS).⁷ In a prospective, single-blind, randomized, controlled trial, 8 weeks of physical therapy — which in one group of patients selectively emphasized retraining of the vastus medialis, and in another group, emphasized general strengthening of the quadriceps — proved superior to the provision of no treatment, for pain reduction and improvement in subjective function and quality of life. The investigators suggested that selective physical therapy may be appropriate early in rehabilitation.

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 of 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 orthoses, which in turn can lessen knee pain.

Foot orthoses are often of benefit in returning the subtalar joint to a nearly neutral position; this reduces foot pronation, thereby decreasing rotational forces in the tibia that affect tracking of the patella during locomotion.⁸ Improvement in quality of life measures has been demonstrated following provision of custom orthoses to individuals with PFS and excessive foot pronation.

One study compared the effectiveness of off-the-shelf foot orthoses in the treatment of PFS pain with that of either flat inserts or physical therapy; the report also investigated whether the combined use of orthoses and physical therapy is more effective than the employment of physical therapy alone.⁸ The prospective, single-blind, randomized trial utilized 179 patients (including 100 women) between ages 18 and 40 years.

By 6 weeks, patients using orthoses had experienced greater improvement than had persons using flat inserts, but the orthotic group had experienced no significant difference in improvement over patients treated with physical therapy or with a combination of orthoses and physical therapy. By 52 weeks, a significant improvement in patellofemoral pain had occurred in all of the patient groups.

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, because 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 of patellofemoral syndrome 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 of patellofemoral syndrome 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 patellofemoral syndrome resolve with simple measures. As with many exercise routines, patients often fail to adhere to the exercise prescription, producing treatment results that appear to be refractory but which are actually caused by the fact that 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 results that are acceptable or better.

Surgical Intervention

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. 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.⁹

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 patellofemoral syndrome 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 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.

Medication

Two approaches to medicating symptoms of patellofemoral syndrome 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 changes in formulation have been made to reduce the frequency of adverse effects. Selective cyclooxygenase 2 (COX-2) inhibitors have fewer gastrointestinal adverse effects.

Nonsteroidal anti-inflammatory drugs

No NSAID has been found to be more effective in treating symptoms of patellofemoral syndrome 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 adverse effect profiles, and most have the same effect on prostaglandins.

Diclofenac (Cataflam, Voltaren)

Inhibits prostaglandin synthesis by decreasing activity of enzyme cyclo-oxygenase, which in turn decreases formation of prostaglandin precursors.

Dosing

Adult

25 mg PO bid/tid; if well tolerated, increase by 25 or 50 mg at weekly intervals until satisfactory response is obtained or total daily dose of 150-200 mg is reached; higher doses generally do not increase effectiveness

Pediatric

<12 years: Not established
>12 years: Administer as in adults

Interactions

Coadministration with aspirin increases risk of inducing serious NSAID-related adverse effects; probenecid may increase concentrations and, possibly, toxicity of NSAIDs; may decrease effect of hydralazine, captopril, and beta-blockers; may decrease diuretic effects of furosemide and thiazides; may increase PT when taking anticoagulants (instruct patients to watch for signs of bleeding); may increase risk of methotrexate toxicity; phenytoin levels may be increased when administered concurrently

Contraindications

Documented hypersensitivity; do not administer into CNS; patients with peptic ulcer disease, recent GI bleeding or perforation, or renal insufficiency; those at high risk of bleeding

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

Category D in third trimester of pregnancy; acute renal insufficiency, hyperkalemia, hyponatremia, interstitial nephritis, and renal papillary necrosis may occur; increases risk of acute renal failure in patients with preexisting renal disease or compromised renal perfusion; low white blood cell counts occur rarely and usually return to normal in ongoing therapy; discontinuation of therapy may be necessary if persistent leukopenia, granulocytopenia, or thrombocytopenia occurs

Etodolac (Lodine, Lodine XL)

Inhibits prostaglandin synthesis by decreasing activity of the enzyme cyclo-oxygenase.
The decreased activity of cyclo-oxygenase results in decreased formation of prostaglandin precursors, which in turn results in reduced inflammation.

Dosing

Adult

200-400 mg PO q6-8h prn; not to exceed 1200 mg/d

Pediatric

Not established

Interactions

Contraindications

Documented hypersensitivity; do not administer into CNS; patients with peptic ulcer disease, recent GI bleeding or perforation, or renal insufficiency; those at high risk of bleeding

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

Flurbiprofen (Ansaid)

May inhibit cyclo-oxygenase enzyme, which in turn inhibits prostaglandin biosynthesis.
These effects may result in analgesic, antipyretic, and anti-inflammatory activities.

Dosing

Adult

200-300 mg/d PO divided bid/qid

Pediatric

Not established

Interactions

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

Category D in third trimester of pregnancy; acute renal insufficiency, interstitial nephritis, hyperkalemia, hyponatremia, and renal papillary necrosis may occur; patients with preexisting renal disease or compromised renal perfusion risk acute renal failure; leukopenia occurs rarely, is transient, and usually returns to normal during therapy; persistent leukopenia, granulocytopenia, or thrombocytopenia warrants further evaluation and may require discontinuation of drug

Ibuprofen (Motrin, Ibuprin)

DOC for patients with mild to moderate pain. Inhibits inflammatory reactions and pain by decreasing prostaglandin synthesis.

Dosing

Adult

200-400 mg PO q4-6h while symptoms persist; not to exceed 3.2 g/d

Pediatric

<6 months: Not established
6 months to 12 years: 4-10 mg/kg/dose PO tid/qid
>12 years: Administer as in adults

Interactions

Contraindications

Documented hypersensitivity; peptic ulcer disease, recent GI bleeding or perforation, renal insufficiency, or high risk of bleeding

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

Category D in third trimester of pregnancy; caution in congestive heart failure, hypertension, and decreased renal and hepatic function; caution in coagulation abnormalities or during anticoagulant therapy

Indomethacin (Indocin, Indochron ER)

Rapidly absorbed. Inhibits prostaglandin synthesis. Metabolism occurs in liver by demethylation, deacetylation, and glucuronide conjugation.

Dosing

Adult

25-50 mg PO bid/tid
75 mg SR PO bid; not to exceed 200 mg/d

Pediatric

1-2 mg/kg/d divided PO bid/qid; not to exceed 4 mg/kg/d or 150-200 mg/d

Interactions

Contraindications

Documented hypersensitivity; GI bleeding or renal insufficiency

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

Category D in third trimester of pregnancy; acute renal insufficiency, hyperkalemia, hyponatremia, interstitial nephritis, and renal papillary necrosis may occur; increases risk of acute renal failure in patients with preexisting renal disease or compromised renal perfusion; reversible leukopenia may occur (discontinue if persistent leukopenia, granulocytopenia, or thrombocytopenia occurs)

Ketoprofen (Actron, Orudis, Oruvail)

For relief of mild to moderate pain and inflammation. Small dosages initially are indicated in small and elderly patients and in those with renal or liver disease.
Doses over 75 mg do not increase therapeutic effects. Administer high doses with caution and closely observe patient for response.

Dosing

Adult

25-50 mg PO q6-8h prn; not to exceed 300 mg/d

Pediatric

<3 months: Not established
3 months to 12 years: 0.1-1 mg/kg PO q6-8h
>12 years: Administer as in adults

Interactions

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

Nabumetone (Relafen)

Nonacidic NSAID rapidly metabolized after absorption to a major active metabolite that inhibits cyclo-oxygenase enzyme, which in turn inhibits pain and inflammation.

Dosing

Adult

1-2 g PO qd

Pediatric

Not established

Interactions

Contraindications

Documented hypersensitivity; active peptic ulceration, hepatic impairment

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

Category D in third trimester of pregnancy; elderly may require lower doses; caution in those with hepatic and renal impairment

Naproxen (Aleve, Naprelan, Anaprox, Naprosyn)

For relief of mild to moderate pain. Inhibits inflammatory reactions and pain by decreasing activity of cyclo-oxygenase, which results in a decrease of prostaglandin synthesis.

Dosing

Adult

500 mg PO followed by 250 mg q6-8h; not to exceed 1.25 g/d

Pediatric

<2 years: Not established
>2 years: 2.5 mg/kg/dose PO; not to exceed 10 mg/kg/d

Interactions

Contraindications

Documented hypersensitivity; peptic ulcer disease; recent GI bleeding or perforation; renal insufficiency

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

Oxaprozin (Daypro)

For relief of mild to moderate pain. Inhibits inflammatory reactions and pain by decreasing activity of cyclo-oxygenase, which is responsible for prostaglandin synthesis.

Dosing

Adult

600-1200 mg PO qd; not to exceed 1800 mg/d

Pediatric

Not established

Interactions

Increases toxicity of anticoagulants, aspirin, and diuretics

Contraindications

Documented hypersensitivity; history of GI disease, cardiac failure, renal or hepatic dysfunction, or bleeding disorders

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

Category D in third trimester of pregnancy; may cause dizziness, indigestion, nausea, and abdominal cramps

Piroxicam (Feldene)

Decreases activity of cyclo-oxygenase, which in turn inhibits prostaglandin synthesis. These effects decrease formation of inflammatory mediators.

Dosing

Adult

10-20 mg/d PO qd

Pediatric

0.2-0.3 mg/kg/d PO qd; not to exceed 15 mg/d

Interactions

Contraindications

Documented hypersensitivity; active GI bleeding

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

Category D in third trimester of pregnancy; acute renal insufficiency, hyperkalemia, hyponatremia, interstitial nephritis, and renal papillary necrosis may occur; increases risk of acute renal failure in patients with preexisting renal disease or compromised renal perfusion; reversible leukopenia may occur (discontinue if persistent leukopenia, granulocytopenia, or thrombocytopenia occurs)

Sulindac (Clinoril)

Decreases activity of cyclo-oxygenase, which in turn inhibits prostaglandin synthesis. Results in a decreased formation of inflammatory mediators.

Dosing

Adult

150-200 mg PO bid or 300-400 qd; not to exceed 400 mg/d

Pediatric

Not established

Interactions

Contraindications

Documented hypersensitivity; patients in whom aspirin, iodides, or other NSAIDs induce hypersensitivity; GI bleed; renal insufficiency

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

Category D in third trimester of pregnancy; acute renal insufficiency, hyperkalemia, hyponatremia, interstitial nephritis, and renal papillary necrosis may occur; increases risk of acute renal failure in preexisting renal disease or compromised renal perfusion; low white blood cell counts occur rarely and usually return to normal in ongoing therapy; discontinuation of therapy may be necessary if persistent leukopenia, granulocytopenia, or thrombocytopenia occurs; caution in those with anticoagulation defects and in those receiving anticoagulant therapy

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.

Celecoxib (Celebrex)

Inhibits primarily COX-2. COX-2 is considered an inducible isoenzyme, induced during pain and inflammatory stimuli. Inhibition of COX-1 may contribute to NSAID GI toxicity. At therapeutic concentrations, COX-1 isoenzyme is not inhibited, thus GI toxicity may be decreased. Seek lowest dose of celecoxib for each patient.

Dosing

Adult

200 mg/d PO qd; alternatively, 100 mg PO bid

Pediatric

Not established

Interactions

Coadministration with fluconazole may cause increase in celecoxib plasma concentrations because of inhibition of celecoxib metabolism; coadministration of celecoxib with rifampin may decrease celecoxib plasma concentrations

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

Category D in third trimester of pregnancy; may cause fluid retention and peripheral edema; caution in compromised cardiac function, hypertension, conditions predisposing to fluid retention, severe heart failure, and hyponatremia because celecoxib may deteriorate circulatory hemodynamics; NSAIDs may mask usual signs of infection; caution in the presence of existing controlled infections; evaluate symptoms and signs suggesting liver dysfunction

Follow-up

Further Inpatient Care

The standard procedure for treatment of individuals with patellofemoral syndrome 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 in patients with patellofemoral syndrome. 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.

Inpatient & Outpatient Medications

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

Deterrence

Prevention of patellofemoral syndrome (PFS) 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 in patients with patellofemoral syndrome 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 in cases of patellofemoral syndrome 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 patellofemoral syndrome. In addition, 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 Osteoporosis and Bone Health Center. Also, see eMedicine's patient education article Knee Pain.

Miscellaneous

Medicolegal Pitfalls

The most common medical/legal aspects related to patellofemoral syndrome 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, an 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 patellofemoral syndrome is that the patient remain active and continue 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 goals should include resumption of the patient's preferred activities when this is feasible.

References

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Keywords

patellofemoral syndrome, knee pain, patella, patellofemoral, knee cartilage, patellofemoral pain syndrome, pain behind knee, patellofemoral joint, kneecap pain, patella femoral, patella pain, patella femoral syndrome, PFPS, anterior knee pain, chondromalacia patella

Contributor Information and Disclosures

Author

Patrick J Potter, BSc, MD, FRCP(C), Associate Professor, Physical Medicine and Rehabilitation, The University of Western Ontario; Consulting Staff, Department of Physical Medicine and Rehabilitation, St Joseph's Health Care Centre
Patrick J Potter, BSc, MD, FRCP(C) is a member of the following medical societies: American Paraplegia Society, Canadian Association of Physical Medicine and Rehabilitation, Canadian Medical Association, College of Physicians and Surgeons of Ontario, Ontario Medical Association, and Royal College of Physicians and Surgeons of Canada
Disclosure: Nothing to disclose.

Coauthor(s)

Keith AJ Sequeira, MD, Associate Director of Spinal Cord Medicine, Assistant Professor, Department of Physical Medicine and Rehabilitation, Parkwood Hospital, University of Western Ontario
Disclosure: Nothing to disclose.

Medical Editor

Robert E Windsor, MD, FAAPMR, FAAEM, FAAPM, President and Director, Georgia Pain Physicians, PC; Clinical Associate Professor, Department of Physical Medicine and Rehabilitation, Emory University School of Medicine
Robert E Windsor, MD, FAAPMR, FAAEM, FAAPM is a member of the following medical societies: American Academy of Pain Medicine, American Academy of Physical Medicine and Rehabilitation, American College of Sports Medicine, American Medical Association, International Association for the Study of Pain, Physiatric Association of Spine, Sports and Occupational Rehabilitation, and Texas Medical Association
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Patrick M Foye, MD, FAAPMR, FAAEM, Associate Professor of Physical Medicine and Rehabilitation, Co-Director of Musculoskeletal Fellowship, Co-Director of Back Pain Clinic, Director of Coccyx Pain Service (Tailbone Pain Service: www.TailboneDoctor.com), University of Medicine and Dentistry of New Jersey, New Jersey Medical School
Patrick M Foye, MD, FAAPMR, FAAEM is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation, American Association of Neuromuscular and Electrodiagnostic Medicine, Association of Academic Physiatrists, and International Spine Intervention Society
Disclosure: Nothing to disclose.

CME Editor

Kelly L Allen, MD, Regional Medical Director, IMX-Medical Management Services
Disclosure: Nothing to disclose.

Chief Editor

Consuelo T Lorenzo, MD, Consulting Staff, Department of Physical Medicine and Rehabilitation, Alegent Health Care, Immanuel Rehabilitation Center
Consuelo T Lorenzo, MD is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation
Disclosure: Nothing to disclose.

Further Reading

Related eMedicine topics:
Knee, Extensor Mechanism Injuries (MRI)
Limping Child
Patella Fractures
Patella, Fractures
Patellar Injury and Dislocation
Patellar Tendon Rupture
Patellofemoral Arthritis
Patellofemoral Joint Syndromes

Guidelines:
ACR Appropriateness Criteria Nontraumatic Knee Pain
Knee Pain or Swelling: Acute or Chronic

Clinical studies:
Botox for Non-Surgical Lateral Release in Patellofemoral Pain
Comparing Rehabilitation Programs for Patellofemoral Pain Syndrome

eMedicine Specialties > Physical Medicine and Rehabilitation > Lower Limb Musculoskeletal Conditions

Patellofemoral Syndrome

Introduction

Background

Pathophysiology

Frequency

United States

International

Mortality/Morbidity

Race

Sex

Age

Clinical

History

Physical

Causes

Differential Diagnoses

Other Problems to Be Considered

Workup

Laboratory Studies

Imaging Studies

Other Tests

Procedures

Histologic Findings

Treatment

Rehabilitation Program

Physical Therapy

Occupational Therapy

Recreational Therapy

Medical Issues/Complications

Surgical Intervention

Consultations

Other Treatment

Medication

Nonsteroidal anti-inflammatory drugs

Diclofenac (Cataflam, Voltaren)

Dosing

Adult

Pediatric

Interactions

Contraindications

Precautions

Pregnancy

Precautions

Etodolac (Lodine, Lodine XL)

Dosing

Adult

Pediatric

Interactions

Contraindications

Precautions

Pregnancy

Precautions

Flurbiprofen (Ansaid)

Dosing

Adult

Pediatric

Interactions

Contraindications

Precautions

Pregnancy

Precautions

Ibuprofen (Motrin, Ibuprin)

Dosing

Adult

Pediatric

Interactions

Contraindications

Precautions

Pregnancy

Precautions

Indomethacin (Indocin, Indochron ER)

Dosing

Adult

Pediatric

Interactions

Contraindications

Precautions

Pregnancy

Precautions