ACL Sprain

Learn to fall

The ACL's main role is to stabilize the knee during rotational movement.     Photo: Minnaert/flickr

The injury:
ACL injuries rank as the number one ski injury, representing 17.2 percent of all injuries in the sport, according to a 2012 study published in the American Journal of Sports Medicine. More than 20,000 U.S. alpine skiers damage their knees every year, and most of those injuries involve the ACL.

The ACL itself is one of four main ligaments in the knee, and its main role is to stabilize the knee during rotational movement. Rotating a knee too far to one side or the other, or hyper extending it, can tear or even rupture the ACL. Recovery time ranges from six weeks for a moderate sprain to six months or more for a rupture, which typically requires surgery to repair. One study showed that athletes suffer an ACL tear are seven times more likely to develop osteoarthritis in that knee than athletes who have not injured their ACL.

How to prevent it:
Unfortunately, two recent studies have shown that some people may have a genetic propensity toward injuring their ACLs. A 2005 study showed that people with ACL tears were more than twice as likely to have a first-degree relative who had torn an ACL. In 2009, researchers in South Africa found that women who had torn an ACL were more likely to have mutations in genes that produce collagen, the main building block of ligaments, causing their ACL’s to tear or rupture more easily, jconline.com reported.

Still, there’s quite a lot that can be controlled, particularly when you ski. Carl Ettlinger, president of Vermont Safety Research, has been studying ski safety since the 1960s and has authored dozens of studies on injuries and injury prevention. He says injury prevention boils down to three things: learning to fall correctly, having the proper equipment, and strength training.

“We are the product of millions of years of evolution without skiing,” Ettlinger says. “We haven’t developed the basic instincts to respond to falls with skis attached to our feet.”

Ettlinger has developed guidelines and tutorials to help skiers correct poor form and learn to fall properly. Keeping the hips above the knees and arms forward, for example, helps skiers to avoid falling backward, a situation that commonly leads to ACL injuries. For more information on proper technique, and how to reduce the risk of getting injured on the slopes, read Ettlinger’s online tutorial here.

Advances in equipment, most notably in binding release mechanisms that respond to twisting forces, have helped reduce ACL injuries on the slopes. The KneeBinding touts itself as the only binding with a lateral release that responds to twisting pressures. Ettlinger himself is currently working on a platform designed to respond to ACL-injuring forces.

As for strength training, “it can help, but it can’t eliminate the risk of injury,” says Dr. Robert Johnson, a professor emeritus of orthopedic surgery at the University of Vermont. Johnson recommends doing box jumps to strengthen the core, hamstrings, quads, glutes, and calves. He also recommends learning to land properly by landing softly, with knees bent and in line with the hips, rather than rotated inward or knock kneed.

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