An ankle sprain is a stretching or tearing of a ligament in the ankle.
Ligaments are strong fibrous tissues that connect bone to bone.
Their function is to stabilize the joint. The most common cause of a sprained ankle is an inversion injury. Mild Sprain - A mild sprain has occurred when there is stretching or minimal tearing of the ligaments. In cases of mild ankle sprain, it is possible for a health care provider using specific criteria to avoid the need for an x-ray to rule out a fracture. Moderate Sprain - A moderate sprain occurs when the ligaments are partially torn.