Every day an estimated one out of every 10,000 people sprain their ankle, an injury in which one of the two major ligaments on the outer portion of the ankle is stretched and/or torn.
In the great majority of cases, individuals who see a physician for their injury are instructed on how to reduce pain and inflammation. They may be advised to wear an air cast or participate in physical therapy to strengthen the ankle muscles, in order to make a full recovery.
The remaining population—about 10% of people—develop ankle instability, a condition in which, although the ligament has healed, it has done so in a lengthened position. As a result, the person is prone to a feeling of the ankle "giving out" and to additional sprains. Athletes such as ballet dancers, who already have looser-than-average ligaments, are particularly likely to develop this condition.