Patellofemoral Pain Syndrome

Introduction and prevalence

Patellofemoral pain syndrome (PFPS), commonly known as the runner’s knee, is one of the most common causes of knee pain. The incidence is around 5% and the prevalence ranges from 25% to 40% in physically active individuals with knee pain.

Etiology and Pathophysiology

PFPS can occur in the context of malalignment and muscular imbalance, overactivity and overload, and trauma. Imbalance can be in terms of leg length discrepancies, hamstring and hip musculature tightness, angular or rotational deformities, muscle weakness, and foot pronation abnormalities. In terms of overload of the patellofemoral joint, risk factors include prior fitness level, prior exercise regimen, and high BMI. Injuries, including micro-trauma, to the patella can also give rise to PFPS.

Clinical presentation

Pain is often localized to behind or around the patella and made worse by loading a flexed knee. PFPS often worsens with prolonged sitting or descending stairs.

Physical examination

The most sensitive physical examination finding is pain with squatting. Examining the gait, posture, and footwear can help identify contributing causes. Special tests for PFPS include patellar tilt, patella alta, and apprehension tests.

  • In the patellar tilt test, the physician pushes the patellar medial surface posteriorly and the lateral surface anteriorly; the patella should tilt 15 degrees on medial and lateral side.

  • In the patella alta test, the patella is visually and often radiographically observed for a superiorly positioned patella.

  • In the patellar apprehension test, the physician grasps the patella and moves it medially and laterally, with a positive test being a sense of dislocation at lateral translation.

Investigations

Plain radiograph should be ordered if the patient does not respond to conservative therapy, in order to rule out bipartite patella, osteoarthritis, loose bodies, patellar fractures, and osteochondritis. CT and MRI are not recommended in the evaluation of PFPS unless clinically PFPS is unlikely.

Management

Studies have shown that proper rehabilitation can completely resolve PFS symptoms in up to two-thirds of patients. Conservative therapy includes rest, ice, analgesics, NSAIDs, and importantly, physical therapy. Physical therapy should focus on strengthening the hip, trunk, and knee musculature. Patellar taping and foot orthotics have been shown to decrease the overall pain. Conservative therapy should be attempted for 24 months before operative interventions are considered.