1. Background

• most patients show a mild degree of patellofemoral malalignment which with activity causes instability of the patella and gradual destruction of the patellar cartilage
• considered an overuse syndrome not involving avascular necrosis or an inflammatory process (develops over a period of time)
• usually unilateral but at times bilateral

1. Knee

• pain - anterior, underside of patellae, acute and chronic
• crepitance - worse with flexion (climbing stairs, running)
  • detected with manipulation of patellae
• instability - unable to keep knee in flexed position for any length of time, history of knee giving out
• positive patellar inhibition test - patient refuses to actively extend knee when patellae compressed against the femoral condyles - displacement of patellae with knee extension
• no decreased range of motion of affected knee
• chronic pain may result in disuse atrophy of the quadriceps

1. Imaging Studies

1. Conservative

• rest (+/- long-leg cast)
• limitation of activities requiring flexing of knee
• isometric quadricep exercises to strengthen quadriceps

2. Medical

• pain control, NSAID

3. Surgical

• arthroscopy to remove bony or cartilaginous fragments or to shave the underside of the patellae