patella dislocation

Clinical manifestations

• immediate pop may be noted
• patients often able to correct dislocation themselves
• large knee effusion preventing full knee extension
• tenderness to palpation over the medial patella
• positive patellar apprehension test
  • patient stops examiner from pushing the patella laterally due to apprehension

Differential diagnosis

• anterior cruciate ligament tear
  • positive Lachman test
• medial collateral ligament (MCL) sprain/tear
  • medial joint line tenderness, joint swelling
  • rarely large effusion
• medial meniscus tear
  • McMurray test often positive
  • effusions, if any, generally small

More general terms

• joint dislocation

Additional terms

• patella (kneecap)