INTRODUCTION: Ski boots are designed to transfer high forces from the skier to the ski. For this purpose, they are made of rigid materials and constrain the leg of the skier in an unnatural position. To overcome the problem of unnatural knee posture, the ski boots can be adjusted in the frontal plane, as well as in the horizontal plane, by the canting mechanism and the "v-position," respectively. Canting enables lateral and medial orientation of the shaft with respect to the base of the boot. The "v-position" is a pronounced outward rotation of the boot's base with respect to the ski's long axis. The purpose of this study is to investigate the effect of different foot rotations and ski boot canting settings on knee kinematics during standing and simulated skiing. METHOD: Knee kinematics were measured by means of motion analysis along with the help of skin mounted markers on 20 subjects. First, the subjects had to perform eight knee flexion-extension cycles to define the individual knee varus-valgus and internal-external rotation angles without the ski boot Intervention. Thereafter, the subjects put on skis and ski boots and performed firstly an upright standing position-this occurs frequently during resting periods or lining up for the ski lift-and then a skiing position as it occurs during a turn. Both postures were carried out on a compensator to standardize the centre of mass for each subject. The Ski boots were firmly tightened and the ski bindings were adjusted according to ISO 11088. To vary the rotation of the foot in the shoe, a commercially available 9° rotated shoe was used. A conventional shoe counterpart with a foot alignment of 0° was chosen based on the same shaft rigidity measured according to IAS Guidelines (IAS 1980). The canting was set to maximal medial neutral and maximal lateral. RESULTS: The ski boots in their Standard settings significantly constrained the skier to an unnatural valgus position. Ski boot base rotation had a significant effect on internal external knee rotation, whereas canting had an effect on varus-valgus angles during standing. However, for the simulated skiing position no effects were observed. CONCLUSION: The study suggests that the constraints of the ski boots result in a clinically relevant valgus misalignment. Canting settings reduced the misalignment, but only by about 10 %. Increased ski boot canting settings would therefore be desirable. The knee kinematics showed that rotational misalignment could not be linked to any significant increase in injury risk.
© Copyright 2007 4th International Congress on Science and Skiing. Veröffentlicht von University of Salzburg. Alle Rechte vorbehalten.