The unhappy triad (O'Donoghue's triad) of the knee involves which three structures?
- A ACL, posterior cruciate ligament, and lateral meniscus
- B PCL, lateral collateral ligament, and lateral meniscus
- C ACL, medial collateral ligament, and medial meniscus ✓
- D ACL, lateral collateral ligament, and lateral meniscus
Correct answer: C. ACL, medial collateral ligament, and medial meniscus
Explanation
The unhappy triad (valgus stress + rotation injury common in football/contact sports) involves the anterior cruciate ligament (ACL), medial collateral ligament (MCL), and medial meniscus. The medial meniscus is more commonly injured than the lateral meniscus in this injury because it is more firmly attached to the medial capsule and MCL, making it less mobile and more susceptible to tearing when the knee is forced into valgus. The lateral meniscus is more mobile due to less capsular attachment.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.