The head (caput) forms the enlarged proximal end of the fibula. It bears two main landmarks: an apex/processus styloideus which projects proximally from its posterior surface, and a small, medially oriented articular surface for the lateral condyle of the tibia, which contributes to the articulatio tibiofibularis superior. The corpus fibulae forms a long thin shaft, with three surfaces (facies medialis/lateralis/posterior) separated by three ill-defined borders (margo anterior/posterior/medialis). The facies medialis fibulae is marked by a crista interossea, which is connected to the margo interossea tibiae via the membrane interossea cruris to form the middle tibiofibular joint (junctura tibiofibularis intermedia). The distal end of the fibula articulates once again with the tibia to form the articulatio tibiofibularis inferior (syndesmosis tibiofibularis), before expanding to form the malleolus lateralis which constitutes the lateral ‘knob’ of the ankle. Like its medial counterpart, the malleolus lateralis articulates with the corpus tali to collectively form the articulatio talocruralis.
