Refers to an injury of the knee involving pain at or around the patella.
Common knee problem in runners, other athletes and after injury or surgery around the knee.
Accounts for 11 to 17% of all knee pain.
Typically affects active people younger than 40 years of age.
Prevalence in the general population is approximately 22.7% and 28.9% in adolescents.
Quadriceps strength is protective.
Symptoms can persist for years.
Patellofemoral pain around or under the kneecap worse with squatting, running, prolonged sitting, going up or down stairs, or any other activity involving repeated bending of the knee.
The term refers to pain that is not caused by a structural problem with the tendons, ligaments, or cartilage around the knee.
The patella sitting on top of the femur tracks and glides over the knee in various directions as different muscles pull on it.
Proposed mechanisms include abnormal loading of the patellofemoral joint due to patellar maltracking or muscle imbalance, or increased patella intraosseous pressure.
Patellofemoral pain is believed to occurs when there is maltracking of the patella.
Maltracking leads to abnormal contact pressures and mechanics between various parts of the knee.
Maltracking can be caused by external factors including overuse, errors in training, or improper shoes.
Internal factors related to maltracking include imbalances in the strength of the muscles around the knee as well as the hip, an overly mobile kneecap, or a tight iliotibial band.
Patients generally present with gradual onsetanterior knee pain, aggravated by loading a flexed knee such as climbing stairs.
Pain is rarely present when the patellofemoral joint is unloaded, such as with sitting.
Patellofemoral pain is a clinical diagnosis, and imaging tests of the knee, are not needed to make the diagnosis.
Examination of the Patellofemoral Joint:
Persons at risk for patellar instability may exhibit generalized ligamentous laxity & poorly developed vastus medialis; when these patients are sitting or standing erect in a relaxed position patellae often faces laterally
“J sign” – refers to lateral patellar deviation during terminal knee extension.
A quadriceps contracture will cause a reverse “J” sign w/ habitual dislocation of the patella in flexion;
Patellar displacement, the patella can normally be manually displaces both medially and laterally between 25% and 50% of width of the patella.
Greater movement indicates loose patellar restraints, a finding frequently seen in adolescent females.
Patellar compression test:attempts to correlate anterior knee pain w/ articular degeneration;
Compresses the patella down into the trochlear groove as the patient flexes and extends the knee;
Apprehension test: examiner holds the relaxed knee in 20 to 30 deg of flexion, & patella is manually subluxed laterally.
Differential diagnosis of patellofemoral pain, include patellar, tendonopathy, patellar subluxation, Osgood-Schlatter disease, or systemic rheumatic disease.
Anterior knee pain during a squat is the most sensitive test for diagnosis of patellofemoral disease.
X-rays and MRI typically are normal in cases of patellofemoral pain, and are useful only for ruling out other causes of knee pain.
Ultrasound is 85% sensitive and 100% specific for patellofemoral pain when MRI is not available or contraindicated.
There is no key finding on clinical examination to diagnose patellofemoral pain.
Treatment includes: rest, activity modification, and correcting underlying causes such as improper shoes, or errors in training.
Physical therapy is also a mainstay of treatment.
Supervised hip and knee exercises in combination with foot orthosis, or patellar taping or first line treatment.
Nonsteroidal anti-inflammatory drugs or acetaminophen may be helpful.
Knee braces have been shown to help with symptoms for some patients.
A problem of pain and function rather than a structural problem.
No long-term consequences for the knee joint occur.
There is a little evidence of benefit for taping, acupuncture, nonsteroidal anti-inflammatory drugs, nutraceuticals, such as glucosamine, injections of hyaluronic acid, arthroscopy, and surgery.