The medial surface of the lower extremity of tibia
is prolonged downward to form a strong pyramidal process, flattened from without inward - the medial malleolus
- The medial surface of this process is convex and subcutaneous;
- its lateral or articular surface is smooth and slightly concave, and articulates with the talus;
- its anterior border is rough, for the attachment of the anterior fibers of the deltoid ligament of the ankle-joint;
- its posterior border presents a broad groove, the malleolar sulcus, directed obliquely downward and medialward, and occasionally double; this sulcus lodges the tendons of the Tibialis posterior and Flexor digitorum longus.
The summit of the medial malleolus is marked by a rough depression behind, for the attachment of the deltoid ligament.