ACL Injuries from Alpine Skiing
Anterior Cruciate Ligament (ACL) Sprains are the second most common injury for Alpine Skiers today. Approximately ten to fifteen percent of ski injuries that occur are ACL injuries-and this number may actually be higher because many ACL injuries are actually misdiagnosed as the more prevalent but less serious MCL injury.
Today, it is thought that there are three main identified actions that cause Alpine Skiers to sustain ACL injury: the Backward-Twisting Fall, the Forward-Twisting Fall, and the Boot-Induced Anterior Draw.
The Backward-Twisting Fall, also called the Phantom Foot or the Flexion-Internal Rotation, is thought to account for 3/4 of all ACL injuries from Alpine Skiing. You'll recognize this action: it occurs when the back end of the ski acts to apply a combination of twisting and bending forces at the knee joint, often resulting in a backwards fall and a sprain of the ACL.
Research has concluded that there are several actions that can result in this Backward-Twisting Fall. They include:
1. Attempting to get up whilst still moving after a fall
2. Attempting a recovery from an off-balance position
3. Attempting to sit down after losing control
The Forward-Twisting Fall, or the ‘‘valgus-external rotation," has become a more common action as more and more Alpine Skiers are using skis specifically designed for carving. For example, this motion occurs when a skier shifts his or her weight forward relative to the ski (such as while cutting an edge while turning). This bending motion causes the leg to twist and rotate outwards. If the force is great enough it can cause the ACL to sprain
Finally, the last major action that we've identified as being a main cause of ACL injury is the Boot-Induced Anterior Draw. This action occurs when a skier lands off balance with the majority of their weight to the rear of their skis after a jump. If the skier extends his or her legs fully, he or she may land on the tail of the ski, causing the back of the boot to cause pressure against the calf. This in turn pushes the tibia forwards relative to the femur, causing damage to the ACL. There are, of course, other situations where this may occur, but the main mechanism is the extreme pressure on the back of the calf.
Most skiers who have damaged their ACL report hearing a loud POP or SNAP and then feeling their knee give away underneath them. If you believe you may have sprained your ALC, a trip to the doctor is necessary. The doctor will need to take a scan of your joint to discern whether the damage is soft tissue or bone and give a proper diagnosis.
As opposed to the MCL injury, the ACL injury usually requires ligament repair surgery if the skier wants to maintain the same or a similar level of activity after injury. But, most all doctors agree that the rehabilitation and physical therapy both before and after any surgery is as, if not more, important than the surgery itself.
As always, the best course of action is to avoid injury in the first place. We recommend that you maintain a good level of physical conditioning both during the ski season and during the off-season, that you understand these high-risk motions and actions to attempt to avoid them, and that you make sure that your ski equipment and particularly your ski bindings are in good working order.
Avoid these high-risk situations and you may just save your ACL:
1. Don't fully straighten your legs when you fall. Keep your knees flexible.
2. Don't try to get up until you've stopped sliding. When you're down, stay down.
3. Don't land on your hands. Always keep your arms up and forward.
4. Don't jump unless you know where and how to land. Land on both skis and keep your knees flexible.