Malleolus

The malleoli are rounded bony prominences on each side of the ankle. The term refers to two major structures: the medial malleolus, a projection of the distal tibia, and the lateral malleolus, the distal end of the fibula. The name malleolus comes from Latin malleolus, meaning a small hammer, reflecting their peg-like shape.

Anatomy and function

The medial malleolus forms part of the ankle mortise and contributes to medial stability of the ankle joint. The lateral malleolus extends farther distally and provides lateral ankle stability by forming the lateral wall of the mortise. Together, they help constrain the talus within the ankle and serve as attachment points for ligaments. The deltoid ligament attaches to the medial malleolus, while the lateral ligaments—anterior talofibular, calcaneofibular, and posterior talofibular—attach to the lateral malleolus. The medial malleolus also presents articular surfaces for interaction with the talus and, on occasion, a groove for tendons behind it.

Pathology

Fractures of the malleoli are common in ankle injuries. Isolated fractures can involve either the medial or lateral malleolus; combined involvement yields bimalleolar fractures. A posterior malleolar fragment refers to a posterior tibial fragment that may accompany malleolar injuries. A trimalleolar fracture includes fractures of the medial and lateral malleoli plus the posterior tibial fragment. Accurate assessment is essential because the pattern influences stability and treatment.

Diagnosis and treatment

Imaging typically includes radiographs with ankle, including a mortise view; computed tomography may be used for complex fractures. Treatment depends on fracture pattern and alignment: nondisplaced fractures may be managed conservatively, while displaced or unstable fractures commonly require surgical fixation with screws and/or plates, followed by rehabilitation.