Unhappy triad

Musculoskeletal system

Other disorders

Summary

An unhappy triad, also known as O'Donoghue's triad, is a common injury that occurs in the knee joint. It involves damage to the anterior cruciate ligament (ACL), medial collateral ligament (MCL), and medial meniscus. The injury usually occurs as a result of a sudden forceful twist or impact on the knee joint, such as during a sports activity. The lateral meniscus may also be involved in some cases. This injury is typically treated with surgery and physical therapy.