Ankle Sprain

An ankle sprain is a common injury and usually results when the ankle is twisted, or turned in (inverted). The term sprain signifies injury to the soft tissues, usually the ligaments, of the ankle. This guide will help you understand how an ankle sprain occurs, how we diagnose the condition, and what can be done to treat ankle sprains.

What Part of the Ankle is Involved?

Ligaments are tough bands of tissue that help connect bones together. Three ligaments make up the lateral ligament complex on the side of the ankle farthest from the other ankle. They are the anterior talofibular ligament (ATFL), the calcaneofibular ligament (CFL), and the posterior talofibular ligament (PTFL). See Ankle Anatomy for more details. The common ankle sprain usually involves two ligaments, the ATFL and CFL. Normally, the ATFL keeps the ankle from sliding forward, and the CFL keeps the ankle from rolling inward on its side.

What Causes an Ankle Sprain?

Ankle ligaments are made up of multiple strands of connective tissue, similar to a nylon rope. A sprain results in stretching or tearing of the ligaments. Minor sprains only stretch the ligament. A tear may be either a complete tear of all the strands of the ligament or a partial tear of only some of the strands. The severity of a sprain depends on the degree that the ligaments have been weakened. Most ankle sprains (type I and type II) are treated by immobilization. However, a complete disruption (type III sprain) of an ankle ligament or ligaments may require reconstructive surgery.

The lateral ligaments are by far the most commonly injured ligaments in a typical ankle sprain. This is called an inversion injury. The ankle tilts inward, meaning the bottom of the foot angles toward the other foot. This forces all the pressure of your body weight onto the outside edge of the ankle. As a result, one or more of the ligaments on the outside of the ankle (ATFL, CFL, and PTFL) are stretched and possibly torn.

Ankle Syndesmosis Injuries

A severe form of ankle sprain, called an ankle syndesmosis injury, involves damage to other supportive ligaments in the ankle. In an ankle syndesmosis injury, at least one of the ligaments connecting the tibia and fibula bones is sprained. This type of ankle injury is sometimes called a high ankle sprain. It involves the ligaments above the ankle joint. Recovering from even mild injuries of this type takes at least twice as long as from a typical ankle sprain.

Related Ankle Injuries

A sprained ankle can often mask damage to other structures in addition to the ankle ligaments. These related ankle injuries include dislocation or rupture of the peroneal tendons, stress fractures, or osteochondral fractures of the dome of the talus. Such injuries are frequently not diagnosed and thus cause ankle pain that persists much longer than would be expected with a straightforward ankle sprain. Diagnosis and treatment depend on an understanding of the ligamentous and muscular structures around the ankle.