O’Donoghue unhappy triad is occurrence of 3 different soft tissue injuries of knee simultaneously. It includes:
Mnemonic: MAM
- Medial collateral ligament injury
- Anterior cruciate ligament injury
- Medial meniscus injury (associated with lateral compartment bone bruise)
Mechanism: valgus stress with rotation of the knee
Later on, more studies emerged showing that injuries in the lateral meniscus were more prevalent than injuries in the medial meniscus. The unhappy triad changed since its description by O’Donoghue. Being first described as a rupture in the ACL, MCL and medial meniscus, the latter was replaced by the lateral meniscus as a more frequent presence in this triad. Studies are now showing that due to the association of the triad with lesions of the anterolateral complex this is now a tetrad.