A 43-year-old man suffered an irreducible posterolateral knee dislocation while snowboarding with associated tears of the anterior cruciate, posterior cruciate, medial collateral, and posterolateral corner ligaments. Two closed reduction attempts failed, and magnetic resonance imaging revealed incarcerated soft tissue from a tertiary gastrocnemius muscle head. The patient underwent open reduction and repair/reconstruction of his multiligamentous knee injury. At the 6-year follow-up, the patient did not have pain or instability and returned to recreational activities.
This case demonstrates that a tertiary gastrocnemius muscle head, the most common anatomical variation, may complicate the closed reduction of an irreducible posterolateral knee dislocation.