Wide Skis As a Potential Knee Injury Risk Factor in Alpine Skiing

Abstract

Alpine skis with wider waist widths have recently become more popular. With such skis, the contact point of the ground reaction force during ski turns is displaced more medially from beneath the sole of the outer ski, which may present an increased risk of injury. The aim of this study was to investigate knee joint kinetics, kinematics, and lower limb muscle activation as a function of changes of the ski waist width in a laboratory setting. A custom skiing simulator was constructed to enable simulation of different ski waist widths in a quasi-static ski turn position. An optical system was used for capturing knee joint kinematics of the outer leg, whereas a force plate was used to determine the ground reaction force vector. The combination of both systems enabled values for external torques acting on the knee joint to be calculated, whereas electromyographic measurements enabled an analysis of knee flexor muscle activation. With respect to the outer ski, the knee joint external torques were independent of ski waist width, whereas knee joint external rotation and biceps femoris activation increased significantly with the increase of the ski waist width. Skier muscle and kinematics adaptation most probably took place to diminish the external knee joint torque changes when the waist width of the ski was increased. The laboratory results suggest that using skis with large waist widths on hard, frozen surfaces may change the load of knee joint surfaces. However, future research is needed to clarify if this may result in the increased risk of knee injury.

Impact of ski geometry data and standing height ratio on the ACL injury risk and its use for prevention in recreational skiers

“…Notably, tail width failed to reach statistical significance with p=0.082. These results do not confirm other work suggesting that skis with larger waist widths are associated with an elevated risk for injury on hard snow 29 32. In competitive skiing, the International Ski Federation (FIS) regulated in most disciplines the maximal waist width to be typically ≤65 mm 32.…”

“…Previous work has started to examine the relationship between ski width and knee injury. For wider skis, the contact point of the ground reaction force during ski turns is displaced more medially beneath the sole of the outer ski 29. In a study with expert skiers conducted on hard and frozen snow conditions on a ski slope, Zorko et al 10 found that an increased ski width at the waist reduced the mean abduction (knee valgus) and increased external rotation of the lower leg of the outer ski.…”

“…Wider skis are primarily built for off-piste skiing with softer snow conditions or powder snow where a ski sinks into the soft snow surface and then causes a change in the point of application of the ground reaction forces 10. In a recent laboratory study, Zorko et al 29 assumed that the alignment of the ground reaction force with respect to the centre of the knee joint changes with different ski widths, and therefore, the torque applied to the knee would differ. However, with respect to the outer ski knee joint, external torques were independent of ski waist width while knee joint external rotation increased significantly with the increase of ski waist width 29.…”

“…In a recent laboratory study, Zorko et al 29 assumed that the alignment of the ground reaction force with respect to the centre of the knee joint changes with different ski widths, and therefore, the torque applied to the knee would differ. However, with respect to the outer ski knee joint, external torques were independent of ski waist width while knee joint external rotation increased significantly with the increase of ski waist width 29. Interestingly, both studies by Zorko et al 10 29 showed an increase in external rotation of the lower leg with increasing waist widths of the ski which could be connected to the fact that the most commonly self-reported ACL injury mechanism in recreational skiing is the forward twisting fall with a valgus external rotation of the knee joint 12 30 31…”

Monitoring the Performance of Alpine Skiers with Inertial Motion Units: Practical and Methodological Considerations

“…To a certain extent, this latter problem can be attenuated by smoothing/maintaining the track between runs. In addition, accurate geodetic GNSS systems can help ensure that the course gates are placed in exactly the same locations on several days in a row [73]. In any case, snow conditions, which can significantly affect the level of friction between the skis and ground [4], length of the course, shape of the turns, speeds, etc., must be carefully monitored, especially when investigating performance [22,58].…”