A 18-year-old male soccer player had painful triggering and occasional locking of the great toe caused by entrapment of the flexor hallucis longus tendon within the flexor sheath posterior to the right medial malleolus. After other treatment modalities failed, the condition was relieved by a surgical procedure that removed the nodule on the flexor hallucis longus tendon and the ganglion under flexor retinaculum. Tendon rupture was not found, although there was tendinitis.