“Knee injuries are a fact of life in any sport, but over the past 40 years serious knee sprains, usually involving the 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,” Carl Ettlinger, president of Vermont Safety Research in Underhill, Vt. told SnoCountry.com.
Noting we grow more confident as the season progresses and that heavier, spring snow can actually present more opportunities for injury, he said, “Now is a good time” for some prevention tips.
Based on a 40-year study by researchers Dr. Robert Johnson of the Department of Orthopedics at the University of Vermont (UVM), Dr. Jasper Shealy, professor at the Rochester Institute of Technology, and himself, Ettlinger said there is plenty the average skier can do to prevent knee injury and specifically ACL tears.
He stressed that because there is a “chain of events” that leads up to knee injuries, they can be prevented if participants avoid certain risky behaviors and learn how to recognize the situations in the chain itself so they can quickly self-correct. Studies have shown this approach to reduce ACL sprains by more than half.
Understanding Injury Scenario
One situation that leads to an ACL injury is called the “Phantom Foot” as it involves the tail of the ski. During certain situations, the tail of the ski acts like a lever because it points in a direction opposite that of the human foot.
These situations include: Attempting to get up while still moving after a fall; attempting a recovery from an off-balance position; and attempting to sit down after losing control.
Such situations make one vulnerable to Phantom Foot injuries because “the tail of the downhill ski in combination with the stiff back of the ski boot acts as a lever to apply a unique combination of twisting and bending loads to the knee,” Ettlinger explains, noting such loads can partially or completely tear the ACL.
The six elements that create the Phantom Foot profile and most often precede an ACL injury include:
uphill arm back; skier off-balance to the rear; hips below the knees; uphill ski unweighted; weight on the inside edge of downhill ski tail; and upper body generally facing downhill ski.
To reduce the risk of Phantom Foot ACL injury, skiers should routinely correct poor technique; learn to recognize these potentially dangerous situations; and employ corrective responses, such as “arms forward, feet together, and hands over skis.
“The Boot Induced ACL injury is probably the simplest to avoid,” Ettlinger noted. “The injury is sustained during hard landings by off-balance skiers. Typically, the skier begins a jump off-balance to the rear, and rotates the downhill arm up and rearward in an attempt to regain balance before landing. This motion is instinctively coordinated with the extension of the skier's uphill leg.
“When the skier lands, the tail of the uphill ski hits first. As the center of pressure of the snow against the bottom of the ski moves forward, the pressure of the boot against the back of the leg increases, while at the same time, the muscles of the skier's leg automatically contract to hold the leg in a fully extended position. By the time the portion of the ski under the boot heel hits the snow, there is no laxity left in the system to absorb the jarring impact and the back of the boot is able to drive the tibia out from under the femur, thereby tearing the ACL.”
To avoid this type of injury, Ettlinger advises: Avoid any type of aerial maneuver which could leave you off-balance on landing; don't jump unless you know where and how to land; land on both skis, if possible, and keep your knees flexed.
A recent in-depth SnoCountry.com article tells of an alternative treatment for ACL injuries, pioneered by Colorado Dr. Christopher Centeno, a specialist in regenerative medicine and the clinical use of mesenchymal stem cells in orthopedics. Dr. Centeno also offers suggestions on ways to prevent knee injuries.
“While you may have heard that you need to make sure your quads are strong to protect the knee, what you may neglect is that your quads anchor in the front of your pelvis, so a weak core is as bad for your knees as weak quads. Focus on core building exercises such as plank, squats, and balancing core exercises that utilize a Bosu ball.
“Recent studies have shown that women are more likely to injure their knee ACL during ovulation, so women may want to consider this potential time of risk. Being in tune with the natal cycles of your body and when it may be vulnerable is an often over looked method of injury prevention. (http://www.regenexx.com/2013/12/womens-soccer-acl/)
“Believe it or not, knee arthritis is worse in people with metabolic syndrome (i.e. overweight, high blood pressure, high triglycerides) not because they’re heavier, but because their body chemistry can chew up cartilage. So, taking good care of yourself — eating right, maintaining a healthy body weight — will make you feel better and prevent injuries.
“Athletes with chronic low-back problems are more likely to injure their knees in our experience, so don’t forget that the back bone is connected to the knee bone. Focus strength-building exercises on the lower back, glutes [gluteal muscles], and hamstrings.
“Flexibility is also key. Strength building programs that include Yoga, Pilates, balancing exercises, and core strength exercises will all contribute to a stronger body and lessen the chance of knee injury," said Dr. Centeno.
Recreational skiers may be able to avoid the agony of the ACL injury if we take lessons to learn proper stance and technique and follow the tips offered by Ettlinger and Dr. Centeno.
Top Photo: Spring skiing at Big Sky, Mont. (Big Sky); Left: Carl Ettlinger