A 16-year-old girl twists her right knee while skating. The patella dislocates laterally and reduces spontaneously as she straightens the leg. MRI subsequently shows fluid in the joint and oedema along the medial border of the patella extending to the medial femoral epicondyle. The primary structure injured in this event is:
- A Medial collateral ligament of the knee
- B Medial patellofemoral ligament ✓
- C Patellar tendon
- D Lateral retinaculum
Correct answer: B. Medial patellofemoral ligament
Explanation
Traumatic lateral patellar dislocation tears the medial patellofemoral ligament, the main restraint to lateral translation, giving marrow and soft tissue oedema along the medial patella and medial femoral epicondyle. The medial collateral ligament spans the joint line from femoral epicondyle to tibia and is injured by valgus force, not by patellar dislocation. The lateral retinaculum is strained rather than torn here, and the extensor mechanism stays intact.
Reference: Miller's Review of Orthopaedics, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.