Nontraumatic chronic subcutaneous rupture of the extensor digitorum longus (EDL) tendon is rare. A 66-year-old man, recreational runner, suddenly injured his EDL tendon while walking. We surgically reconstructed the ruptured EDL tendon with a free palmaris longus tendon graft. During the surgery, an osteophyte was found to have penetrated the ankle joint capsule and was considered the cause of the tendon rupture. Active toe extension was restored, and the patient completed a 10-km race at 2 months postoperatively.
EDL tendon reconstruction using a free palmaris longus tendon graft is an effective surgical option for athletes.