A case report of a 12-year-old male with heterotopic ossification of the patellar tendon is presented. He was a baseball player and came to our clinic with the complaint of bilateral gonalgia after exercise. We diagnosed the case as Osgood-Schlatter disease. Inspite of the conservative treatment, a fragment was separated from the tibial tuburcle. The ossicle moved to the central portion of the patellar tendon, increasing its size.
