Peroneal tendonitis, or peroneal tendinopathy, is a condition that is characterised by pain or tenderness on the outside or back of the ankle. While usually caused by the overuse of the tendon, it is sometimes caused by an acute injury.
The peroneal tendon consists of two tendons, the peroneal brevis tendon and the peroneal longus tendon, that are attached to different parts of the foot. The main function of these tendons is to evert and pronate the foot as well as stabilise the ankle during activities such as walking or running.