A trimalleolar fracture is a fracture of the ankle that involves the lateral malleolus, the medial malleolus, and the distal posterior aspect of the tibia, which can be termed the posterior malleolus.

The trauma is sometimes accompanied by ligament damage and dislocation.

Strictly speaking, there are only two malleoli (medial and lateral), but the term trimalleolar is used nevertheless and as such is a misnomer.

Surgical repair using open reduction and internal fixation is generally required, and because there is no lateral restraint of the foot, the ankle cannot bear any weight while the bone knits.

Non-surgical treatment may sometimes be considered in cases where the patient has significant health problems or where the risk of surgery may be too great.