History of a foot inversion with flexion (most common mechanism) involves the lateral ankle (distal fibular avulsion fracture). Eversion forces with dorsiflexion avulse the medial malleolus.

Ankle fractures are associated with pain, swelling, tenderness, and ecchymosis in association with point tenderness over the medial or lateral malleolus. Ankle fractures can be differentiated from sprains by the physical finding of point tenderness over the lateral malleolus (distal fibula) or medial malleolus. If there is no point tenderness over the malleoli, an x-ray is not necessary. Point tenderness over the lateral ligaments (anterior talofibular and calcaneal fibular ligament) is indicative of an ankle sprain. A first-degree ankle sprain has tenderness only over the anterior talofibular ligament, whereas a secondor third-degree ankle sprain has tenderness over the anterior talofibular ligament and the calcaneal fibular ligament, which lies more posterior.

Three views are required: anteroposterior, lateral, and mortise. The mortise is an oblique view with the foot in approximately 15 degrees of internal rotation. There are three main types of distal fibular fractures: Weber types A, B, and C. The Weber type A fracture occurs below the level of the ankle mortise. (The ankle mortise is the joint space on the mortise view x-ray between the top of the talus and bottom of the tibia.) The Weber type B fibular fracture occurs at the level of the ankle mortise. The Weber type C distal fibular fracture occurs above the ankle mortise. Increased distance between the talus and the medial malleolus is sometimes seen (Fig. 1).