The lateral malleolus is the distal end of the fibula forming the lateral wall of the ankle mortise, reaching about 1 cm lower and lying more posterior than the medial malleolus. It provides attachment for the three lateral ankle ligaments (ATFL, CFL, PTFL) and the inferior tibiofibular ligaments, and a groove on its posterior surface carries the peroneal tendons. Its fracture level relative to the syndesmosis determines the Weber classification (A below, B at, C above the syndesmosis) and directly influences surgical decision-making.
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| Ossification | The lateral malleolus ossification centre (distal fibular epiphysis) appears at about age 1 to 2 and fuses at skeletal maturity around age 15 to 17, slightly later than the distal tibial epiphysis. |
Weber classification of lateral malleolus fractures: Type A (below the syndesmosis, syndesmosis intact, treat conservatively in most cases), Type B (at the syndesmosis, which may or may not be disrupted, assess with stress views), Type C (above the syndesmosis, syndesmosis disrupted, surgical fixation with syndesmotic repair required). The fibula carries only about one sixth of body weight, but its position is critical: 1 mm of lateral talar shift reduces tibiotalar contact area by roughly 40 percent. A shallow posterior groove predisposes to peroneal tendon subluxation. Small avulsions at the ATFL or CFL attachments must be distinguished from lateral talar process fractures. In children, the open distal fibular growth plate should not be mistaken for a fracture.
Feel the bony prominence on the outer side of the ankle; this is the lateral malleolus, the end of the fibula. Its tip reaches about 1 cm lower and sits further back than the medial malleolus. The fibularis tendons run in the groove behind it, and the anterior talofibular ligament runs forward from its front edge.
The most common ankle fracture, usually from inversion or external rotation; Weber classification by fracture level relative to the syndesmosis guides treatment.
Tearing of the superior peroneal retinaculum, sometimes with a small rim avulsion, lets the peroneal tendons dislocate over the malleolus.
