Sprains can be either minor or severe. A minor sprain occurs when a ligament is overstretched or partially torn. A severe sprain occurs when the ligament is completely torn. In very severe sprains, the end of the bone to which the ligament is attached can crack or be pulled off. This is known as an Avulsion Fracture.
Sprains are far worse than a break, and can take months to heal. The most common type of sprained ankle occurs when the foot turns inwards, overstretching the ligaments on the outside of the ankle.
Ankle sprains are very common in sports such as running, jumping, changing direction or stop-start sports.