Peroneus Tertius Tendon Tear Causing Lateral Ankle Pain in a Child.

The peroneus tertius muscle arises in the anterior compartment of the leg and demonstrates significant morphologic variation. Its function is not yet clearly delineated. We present the case of a 12-year-old patient with an isolated tear of the peroneus tertius tendon that resulted in lateral based ankle pain. After surgical reconstruction, the patient's pain resolved, and he was able to return to his normal activities.