When a ligament is overloaded, tearing occurs. These injuries are graded on a scale of 1–3. Grade 1 injury is a stretch without instability; grade 2 is a partial tear with some instability; and grade 3 is a total disruption of the ligament with instability of the joint. The ankle has three lateral ligaments (anterior talofibular, calcaneofibular, and posterior talofibular) and a medial deltoid ligament. Inversion of the foot generally damages the anterior talofibular ligament, whereas eversion injures the deltoid ligament. Lateral ankle sprains are far more common than medial ankle sprains because the deltoid ligament is stronger mechanically than the lateral ligaments. However, medial ankle sprains may have more severe complications, including syndesmotic tearing and instability of the ankle joint requiring surgical stabilization. High ankle sprains involve injury to the tibiofibular syndesmosis, a movable connection in which the adjacent tibia and fibula bones are bound together by ligamentous structures. The syndesmosis supports the integrity of the ankle mortise joint. The ankle mortise is defined as the bony arc formed by the tibial plafond, the medial and lateral malleoli, and the roof of the talus. The mortise provides the wide range of flexibility and motion of the ankle, but its injury causes instability and pain. Syndesmotic injuries do not typically require surgery but do involve longer healing times than low-grade medial or lateral ankle sprains.