ABSTRACT The peroneus quartus (PQ), a supernumerary muscle of the ankle is located in the lateral compartment of the leg. Its most common origin is from the peroneus brevis muscle and insertion into the retrotrochlear eminence of the calcaneus. We observed an unusual variant of the muscle arising from the lateral surface of fibula between the two peroneal muscles. The tendons were crowded beneath an overhanging lateral malleolus. The muscle was found to be inserted onto the peroneal trochlea. The presence of this muscle has been the cause of lateral ankle pain and swelling. It has been implicated in tears and subluxation of peroneus brevis and tenosynovitis of peroneal tendons
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