In brief Syndesmosis ankle sprains, though potentially disabling, often appear benign initially. These sprains are characterized by a rotational mechanism of injury, long recovery, and, frequently, heterotopic ossification. Diagnosis and grading are based on physical exam findings and imaging studies. Treatment ranges from aggressive functional rehabilitation to surgical stabilization. Long-term results can be good if the ankle mortise is anatomically reduced and a synostosis between the tibia and fibula does not form.