Spontaneous Fracture of the Os Peroneum With Rupture of the Peroneus Longus Tendon.

Rupture of the peroneus longus tendon with or without an associated os peroneum fracture is rare and uncommonly encountered in the published data. Owing to the infrequent nature, a high index of suspicion is required. Otherwise, the opportunity for the injury to result in a delayed or missed diagnosis is increased. We report the case of a 39-year-old male with spontaneous rupture of the peroneus longus tendon and associated fracture of the os peroneum. The spontaneous rupture and fracture were diagnosed from the history, physical examination, and imaging findings. The patient elected to undergo operative repair, with excellent results, full recovery, and full return to normal function.