Knee injuries are a fact of life in any sport, but over the past 30-35 years serious knee sprains, usually involving the anterior cruciate ligament (ACL), have become an inherent risk of modern Alpine skiing, with more than 20,000 sustained each year by skiers in the U. S. alone. The ACL, located near the center of the knee, helps to maintain proper alignment of the load-bearing surfaces. Injury to the ACL can result in an unstable knee, which may lead to expensive surgery or a lengthy period of rehabilitation if the injured skier is to resume an active lifestyle.