A footballer sustains a contact injury with a valgus force to the knee followed by forced external rotation. He hears a 'pop' and has immediate effusion with a positive anterior drawer test and positive McMurray's test. The 'unhappy triad' (O'Donoghue) injuries classically involve which three structures?

• A Anterior cruciate ligament, medial collateral ligament, lateral meniscus
• B Posterior cruciate ligament, medial collateral ligament, medial meniscus
• C Anterior cruciate ligament, lateral collateral ligament, lateral meniscus
• D Anterior cruciate ligament, medial collateral ligament, medial meniscus ✓

Explanation

The classic O'Donoghue unhappy triad results from a valgus stress + external rotation mechanism: (1) ACL tears first (prevents anterior tibial displacement); (2) MCL is torn by valgus stress; (3) medial meniscus tears — the medial meniscus is more vulnerable because it is firmly attached to the MCL and joint capsule (less mobile than the lateral meniscus). Positive anterior drawer and Lachman tests indicate ACL injury; McMurray's test localises meniscal tears. Current evidence also notes lateral meniscus injury is actually more common in acute ACL tears, but for NEET PG, the classic O'Donoghue triad remains medial meniscus.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.