A 27-year-old male patient sustained an isolated syndesmotic injury in the right ankle following a fall. His complaints subsided gradually within the first six weeks of conservative treatment. At the end of the third month, he returned to follow-up with posterior ankle pain. Radiological examinations revealed heterotopic ossification adjacent to the posterior inferior tibiofibular ligament and posterior capsule. His complaints disappeared only after local excision of the ossification. Heterotopic ossification may be a cause of persistent pain after ankle ligament injuries.