A 22-year-old athlete twists his knee during football. Examination shows a positive anterior drawer test, positive Lachman test, and a pivot shift. MRI confirms anterior cruciate ligament (ACL) tear with associated medial meniscus tear. Regarding the 'unhappy triad' (O'Donoghue's triad), which three structures are classically involved?

• A ACL, posterior cruciate ligament, and lateral meniscus
• B PCL, medial collateral ligament, and lateral meniscus
• C ACL, medial collateral ligament, and medial meniscus ✓
• D ACL, lateral collateral ligament, and lateral meniscus

Explanation

O'Donoghue's unhappy triad (1950) classically describes injury to the ACL, medial collateral ligament, and medial meniscus from a valgus external rotation force at the knee — typically in contact sports. The medial meniscus is attached to the deep part of the medial collateral ligament (capsular ligament), making it prone to co-injury when the MCL is torn. Contemporary studies show the lateral meniscus is more commonly torn in ACL injuries due to the pivot shift mechanism, but the classic triad in NEET PG examinations refers to the original O'Donoghue description.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.