Posterior colliculus of medial malleolus

The posterior colliculus of the medial malleolus is the smaller of the two bony projections on the distal tibia.

The medial malleolus is the prominent bony landmark on the inner side of the ankle, formed by the distal tibia. On its anterior surface, the medial malleolus presents two small elevations:

• The anterior colliculus (larger and more prominent).

• The posterior colliculus (smaller).

• Between them lies the intercollicular groove for the attachment of the deltoid ligament (medial collateral ligament of the ankle).

Function and Attachments

• The posterior colliculus provides attachment mainly to the posterior tibiotalar fibers of the deltoid ligament.

• These fibers extend from the tibia to the talus and play a crucial role in resisting posterior displacement and external rotation of the talus, contributing to ankle stability.

Clinical relevance

• In ankle fractures, especially medial malleolar fractures, the involvement of the posterior colliculus is used in classification systems (e.g., Herscovici classification).

• The distinction between anterior and posterior colliculi is important in surgical fixation planning, as the posterior colliculus is often less prominent but crucial for ligamentous stability.

• Damage or avulsion at the posterior colliculus indicates possible injury to the posterior tibiotalar component of the deltoid ligament, which may destabilize the ankle mortise.