A 16-year-old male patient applied to our emergency service with right ankle pain following a football injury. His history revealed forced acute hyperplantar flexion. There was a mild swelling at the posterolateral side of right ankle and he had difficulty in walking. Posterior ankle and back of the lateral malleoli were painful by palpation. Os trigonum fracture was detected at lateral X-ray of the right ankle (Figure 1). Fracture was seen more clearly when actual X-rays were compared to the patient's older X-rays which were taken when he presented to our clinic because of ankle sprain two months ago (Figure 2). The patient had been treated with a short leg splint, since no fracture was detected. The splint was removed one week later and joint range of motion and strengthening exercises were started. After three weeks, the patient was fully recovered. A written informed consent was obtained from the legal guardian of the patient.
Os trigonum fracture and surrounding edema were detected by CT and MRI (Figure 3). There was no additional injury. Patient was treated conservatively. A non-weight bearing short leg cast was applied. Union of fracture was seen on sixth week X-ray (Figure 4). Cast was removed after six weeks. Joint range of motion and strengthening exercises were started. The patient was allowed full weight bearing when the cast was removed. Painless and full range of motion was obtained four weeks after cast removal. The patient was followed-up for a total of three months. Nonunion, chronic pain or posterior ankle impingement syndrome was not detected in the patient after the treatment. The patient returned to sports activities without any complaints.