A 27-year-old runner presented to our sports medicine clinic with 4 months of medial foot pain after an eversion ankle sprain. Initial radiographs were negative for fracture. Her symptoms improved but plateaued after 1 month. She was unable to continue running and noticed a new prominence at her right medial foot. Results of a physical examination showed pes planus, a prominent navicular in her right foot and mild weakness of inversion at the right ankle. Magnetic resonance imaging showed bone edema adjacent to a navicular synchondrosis, which confirmed a diagnosis of type 2 accessory navicular with synchondrosis injury. The patient was treated conservatively with a progressive rehabilitation course.