Background: Injuries to ankle joint consist 12% of visits to emergency departments. In spite of the common occurrence of ankle sprain, syndesmosis injuries are rare, but very debilitating and frequently misdiagnosed.

Methods: Among 100 patients with ankle sprain we evaluated the incidence of syndesmosis sprain by MRI of the ankle. Adults who had acute ankle sprain with no fracture and examined on the same day that injury had took place were being included in the survey.

Results: Out of 100 patients with ankle injury, four had syndesmosis sprain. Three patients had partial tear of syndesmotic complex and one had complete tear. All injuries occurred in sports except one which had happened in an accident, and two of the patients were athletes. Anterior inferior tibiofibular ligament was the most common ruptured ligament.

Conclusions: We reported a four-percent incidence of this injury. Our high rate of this injury emphasized on the fact that all suspicious cases should go under more accurate investigation not to miss this diagnosis.