Over the years ski equipment has undergone several different changes to better equip the modern rider in terms of safety. While lower leg and ankle injuries have gone down drastically, knee injuries especially ACL injuries, have increased. The authors of this study hypothesized that posture plays a big role in the cause and prevention of ACL injuries when skiing. It was shown that ACL injuries are directly related to the “anterior drawing force by the quadriceps, in addition to the passive factor of extrusion of the lower leg by the boot”. It’s believed that the violent force of a quadriceps contraction in order to avoid a backward fall is a common mechanism in ACL injuries.
Test subjects for this study were fitted with a ski boot on only one leg and positioned into a force plate at a set inclination angle of 20 degrees. They were then fitted with 40 landmarks of a joint analysis system and a EMG was used to measure muscle activity of the hamstrings and quadriceps. The knee was kept at a constant 30 degree angle at all three postures forward, neutral and backwards. The results of the study showed in a “backward bending skiing posture,
the extension moment of the knee joint and imbalance of muscle contraction of the quadriceps and hamstrings were increased”. The authors suggested that this imbalance and increase of the extension moment in the knee joint may be an important factor to ACL injuries. The results of the present study suggest that “the internal force exerted by the quadriceps, in addition to the passive factor of extrusion of the lower leg by the boot, may contribute to noncontact
ACL injury in a backward bending posture in skiing”.
This is important because many people attribute a tear in the ACL to the knee being locked and the body falling forward. While this is a common way to injure the ACL, this article suggested that a backward bending posture when skiing may be a better way to balance out the muscle contraction of the hamstrings and quadriceps which in turn will balance the force being exerted on the knee joint when skiing.
Knowing this information is a good patient education tool to use in my practice and depending on the location of my practice it may be a useful bit of information to tell any of my patients before they head to the slopes. It is my understanding that chiropractic does not treat patients with injuries to the ACL unless there is a rehab component to the practice. I don’t foresee myself owning a practice where I have a physical therapy element but who knows what the future may hold.
Some of the drawbacks of this study were that they only measured one leg on the force plate while the other was left to dangle next to it. It seems to me that an experienced researcher would want to measure both legs at the same time in order to best simulate a skiing posture. Measuring only one leg at a time may have created more variables that could have gone unnoticed. This can be seen in the forward bending posture photograph, where the leg being measured is in the correct position but the opposite leg is being hyper extended. This is not the normal position of a skier in a forward bending posture and may have led to incorrect results. I however do not believe that the results of this paper impact chiropractic in a negative way because the purpose of this study way to better understand skiing posture and its affect on ACL injuries. This article will help to better educate my patients on proper ways to avoid injuring themselves by using proper techniques on the slopes.
