What causes an Ankle Sprain?

Ankle sprains occur when abnormal forces are sustained at the ankle joint. Eighty-five percent of all ankle sprains involve the lateral (outside) ankle ligaments in which the foot turns inward, rolling over on its outer edge [10]. This is known as an inversion injury. The opposing eversion injury is less likely due to inherent stability by the skeletal structure of the foot and the more robust deltoid ligaments.

Injury to the lateral ankle ligaments tends to occur in a step-wise fashion starting in front of the ankle with the anterior talofibular ligament, which is most prone to injury. This is followed by injury to both the anterior talofibular and calcaneofibular ligaments, and finally involvement of all three lateral ankle ligaments. As the severity of injury progresses, there is a tendency for more instability and inability to bear weight on the affected limb.

It is important to emphasize that not all injuries to the ankle are isolated to its ligaments. Ligamentous injuries are often accompanied by damage to other structures, such as bone, muscle, and/or tendon. For this reason, Fallat et. al. proposed the term “Sprained Ankle Syndrome” to more accurately reflect of the complexity surrounding this type of injury [11].