Introduction: Heterotopic ossification of the Achilles tendon (HOTA) is a rare but consequential complication to an inflammatory event, often presenting challenges in diagnosis and management.
Case Report: We report a case of a 42-year-old male with Type II diabetes mellitus, managed with Metformin, who presented with acute pain and swelling in the right ankle following a running activity. Clinical examination revealed tenderness and a visible swelling proximal to the calcaneum attachment of the tendon which was hard in consistency, and a positive Thompson test indicative of a potential Achilles tendon injury.