**2. Biomechanics**

The lateral ankle compartment comprises the anterior talofibular ligament (ATFL), the calcaneofibular ligament (CFL), and the posterior talofibular ligament (PTFL). The most commonly injured ligament is the ATFL as it is the weakest of all three ligaments. In frequency of injury, the ATFL is followed by the calcaneofibular ligament CFL [3]. The PTFL is rarely injured as it is the strongest of all the three

ligaments. The most common mechanism of injury in lateral ankle sprains is when, in forced plantar flexion, inversion occurs with excessive ankle supination. In that position the ankle joint is the most unstable. In the course of the inversion, the body's center of gravity moves over the ankle leading to ankle sprains [2]. There are three clinical grades of lateral ankle sprains [4–6].

Grade I—Mild. There is an incomplete tear of ATFL with little swelling and tenderness, minimal or no functional loss, and no mechanical joint instability.

Grade II—Moderate. Complete tear of ATFL with or without an incomplete tear of CFL with moderate pain, swelling, and tenderness over the involved structures; some joint motion is lost, and joint instability is mild to moderate.

Grade III—Severe. Complete tears of ATFL and CFL with marked swelling, hemorrhage, and tenderness. There is loss of function, and joint motion and instability are markedly abnormal.
