Chronic instability of the ankle is frequently due to disruption of the fibres of the anterior talofibular ligament and the anterolateral capsule. This allows momentary subluxations at the ankle joint; the talus tilts into an abnormal varus position and rotates forwards and inwards about a vertical axis which passes through the medial malleolus. The use of a free tendon graft to reconstruct the anterior talofibular ligament restores the stability of the ankle without restricting movement at the subtalar level.