The majority of ankle injuries do not involve bony fractures, rather they involve the soft tissue structures of the ankle joint. An ankle sprain is a stretching, partial or complete tear of the ligaments of the ankle. The most common type of ankle sprain is a lateral sprain, usually caused by an inversion injury. Ankle sprains can be classified as a grade I to III, depending on the severity of the injury. A grade I injury is a slight stretching of the ligament; whereas, a grade III sprain is a complete tear of the ligament.