O'Donoghue unhappy triad

Last revised by Joachim Feger on 14 Oct 2020

O'Donoghue unhappy triad or terrible triad often occurs in contact and non-contact sports, such as basketball, football, or rugby, when there is a lateral force applied to the knee while the foot is fixated on the ground. This produces an abduction-external rotation mechanism of injury ("pivot shift" in non-contact sports).


The O'Donoghue unhappy triad comprises three types of soft tissue injury that frequently tend to occur simultaneously in knee injuries. O'Donoghue described the injuries as:

The triad has subsequently been revisited considering the arthroscopic findings in patients with both ACL and MCL injuries, where a lateral meniscal injury is more common than injury to the medial meniscus 2. Mechanistically this makes more sense during the pivot shift movement, as the lateral tibiofemoral compartment is compressed, causing failure of the lateral meniscus.

History and etymology

The unhappy triad is named after D H O'Donoghue, American orthopedic surgeon, who described it in 1950 4.

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