Each year about 20,000 skiers sustain a severe knee sprains. While the incidence of practically every other type of ski injury has declined over the past 20 years, the rate for serious knee sprains that usually involve the anterior cruciate ligament (ACL) has more than tripled. Hundreds of millions of dollars are spent annually treating these injuries and additional millions are spent handling claims. Ski areas feel the pinch in higher insurance rates including Workman’s Compensation.
The bottom line is, no one on Alpine ski equipment is safe from ACL injuries, nothing seems to work and no one is doing anything about it.
Ski injuries overall are down by about 50 percent over the past 20 years according to a study conducted by Dr. Robert Johnson of the University of Vermont Department of Orthopedics and Rehabilitation. His study also shows the once common broken leg and most injuries to the ankle to be down by about 90 percent. Good news for all those who have worked to improve the quality of binding release systems. But none of this seems to help solve the ACL problem. Ski bindings are apparently not part of the problem and may not even be part of the solution.
The ACL is one of four ligaments which make up the knee joint. Its primary function is to maintain proper alignment of the tibia with the femur. Disruption of the ACL can cause chronic instability and progressive damage to the cartilage that form the load-bearing surfaces of the joint. Those who wish to continue an active life (including such activities as skiing) will often require surgery and intense rehabilitation to restore stability and confidence in the joint.
The incidence of ACL sprain, is about one in every 2,000 skiers per day, more frequent even than broken legs at their height in the late 1960’s and on a par with professional football. In comparison, the incidence of ACL sprains among the general population is about one in every 2,000 persons per year. Although the incidence of ACL sprain has stopped rising, it remains the most common injury reported by Alpine skiers today.
A conservative estimate of the average cost of an ACL sprain, considering the full spectrum of treatment options, is about $10,000, which brings the total medical cost nationwide to at least $200,000,000 annually. However, when all factors are considered, the real costs are much higher. The total cost, for example, to return a patrolman or instructor to full, active duty could run to over $60,000.
Although the incidence of lower leg injury has been related to the quality of the release system, the incidence of serious knee sprains is now believed to be related to qualities of the support and control system. Today’s boots and skis are precision instruments, indispensable to modern skiing technique. The stiff back of modern Alpine boots allows skiers to easily weight the rear body of the ski. Today’s skis are particularly effective in carving when weighted and put on edge.
However, this combination of modern boot and ski when attached to the leg of an off balance skier has the potential to over-steer and, in the process, apply a unique combination of loads to the knee. Over-steering can occur when the skier is caught off balance leaning backward and into the hill. Injury to the ACL can result if the skier cannot quickly, and virtually automatically, transfer weight to the uphill ski as the downhill ski carves inward.
This scenario has been termed the “Phantom Foot” ACL syndrome because the lever system that twists and bends the knee—the rear body of the ski—extends from the leg in a direction opposite the natural lever system—the human foot. Although other mechanisms of injury have been identified, the Phantom Foot ACL appears to be the most common.
The information necessary to point the way to practical solutions to the ACL problem could be obtained for a relatively modest cost in a year or two of concentrated effort. To get the industry moving in a direction that will allow normal market forces to accelerate meaningful change, a range of parallel projects designed to determine the feasibility of a variety of ACL protection strategies would be prudent and should include the following:
Fall Analysis — of video tapes of actual knee sprains for the purpose of developing a program that could help reduce the frequency of falls which put the knee at risk.
Accident and Injury Analysis — of existing data in an accelerated effort to gain better understanding of the events leading up to severe knee sprain and the mechanism of injury.
Ski Analysis — of characteristics which may contribute to over-steering.
Boot Analysis — of characteristics which may contribute to over-steering.
ACL Failure Analysis — of the strength of the human knee joint when subjected to Phantom Foot loading.
Retention Analysis — of the frequency and magnitude of loads in skiing of the type found to put the ACL at greatest risk during a fall.
The program outlined above has been proposed by a team headed by Dr. Robert Johnson and including Jasper Shealy of Rochester Institute of Technology and the writer of this article. The concerted effort required for this short-term program would require expenditures in the order of $250,000. Much planning has already taken place and several projects could begin immediately. However, without adequate funding, some issues might never be addressed or the research could drag on for years and delay a clear understanding of the most effective course of action.
To raise the funds required, contributions are sought from companies that profit from this sport and from those who could benefit from a program that would help reduce the risk of this devastating injury. We cannot forever tell ourselves it’s someone else’s problem or hide behind the myth that nothing can ever be done. The current rate of serious knee sprains is a public relations time bomb, a drain on all our resources and, in the light of how little our industry has spent on the problem to date, a moral outrage.
To help us all learn more about ACL injuries in Alpine skiing, contact Dr. Robert Johnson, 922 St. George Rd. Williston, Vt 05495. Contributions should be made to University Orthopedics a non-profit cooperation.
Editor’s note — Carl Ettlinger has researched ski injuries for more than 25 years. Through his laboratory at Vermont Ski Safety Equipment in Underhill Center, he tests products for Skiing magazine where he has been a technical editor since 1973. For the past 20 years, he has worked with Doctors Johnson and Shealy on what has become the largest and longest-running study of ski injuries anywhere.
