A Guide To Prescribing Orthotics For Alpine Skiing
Patients who tackle the slopes have specific requirements for orthotics. In addition to reviewing the pedal mechanics and biomechanics of skiing, our expert panelists take a closer look at the design of ski boots and what impact the skier’s skill level will have on prescribing an appropriate orthotic. Without further delay, here is what they had to say. Q: What pedal mechanics are unique to skiing? A: During alpine skiing, the patient’s lower extremities never go through a complete gait cycle, notes Nicholas Sol, DPM, CPed. He says skiers should ideally have knee flexion during the entire contact cycle, asynchronous single and double limb support, and limited pedal mechanics between midstance and early propulsion. In order to make efficient turns and maintain their balance, skiers must tip both skis onto the corresponding inside and outside edges, according to Brian T. Maurer, DPM, and Michael J. Schneider, DPM. They say the key is maintaining weight and pressure along the inside edge of the downhill ski. When initiating a turn, skiers maintain control by directing the downhill knee medially and transferring the load into the foot over the inside edge. As Drs. Maurer and Schneider note, rotating the tibia internally causes a closed kinetic chain pronation of the foot that transfers the pressure through the boot onto the ski edge. “The higher the level of skier, the more subtle the dynamic,” say Drs. Maurer and Schneider. If the skier has an unstable or overpronated foot, he or she may have difficulty turning as the “medial arch of the foot may collapse within the boot before the edging force can be transferred to the ski edge,” according to Drs. Maurer and Schneider. Q: How is a ski boot different from a walking shoe? A: Unlike most footwear, ski boots do not allow normal gait, according to Drs. Maurer and Schneider. Dr. Sol concurs, noting that alpine ski boots are designed to resist flexion at the MTPJs and limit flexion at the ankle. All of the panelists agree that ski boots are intended to lock the foot in a stable position in order to ensure that direction from the hips, knees and lower legs will be transferred directly onto the edge of the ski. The more rigid the ski boot, the better the ability of the skier to efficiently transfer these forces, point out Drs. Maurer and Schneider. Q: How does a ski boot affect pedal mechanics? A: While rigid ski boots lock the foot and prevent normal gait, Drs. Maurer and Schneider point out that these boots do allow rotational motion of the tibia as the knee is adducted to put pressure over the inside ski edge. Dr. Sol adds that turning the pelvis and torso clockwise causes external rotation of the right leg and outside edging of the right ski while simultaneously causing internal rotation of the left leg and inside edging of the left ski. Ensuring a proper boot fit is essential. Drs. Maurer and Schneider note that skiers with excessive tibial varum will often have significant problems with a boot that is improperly fit. When there is a good fit, the cuff of the boot should align with the position of the tibia. However, if there is not a snug fit of the boot cuff and too much room medially, Drs. Maurer and Schneider point out “there will be an inefficient transfer of force to the ski edge as the tibia and knee move medially.” As a result, they explain that skiers with bowed legs will ride their outside edges and have difficulty turning whereas skiers with knocked knees will ride the inside edges and often have to exaggerate knee movements in order to begin turning. Q: How does one’s skiing level affect pedal mechanics? A: Beginning skiers tend to lean backward and emphasize heel weighting, according to Dr. Sol. He adds that heel weighted skis allow less stability and the least amount of directional control. Drs. Schneider and Maurer concur. They say this tendency in novice skiers can lead to difficulty turning and boot-related injuries such as subungual hematoma, dorsal nerve compression and irritation of bony prominences across the metatarsal-cuneiform joints. More advanced skiers tend to evenly weight and/or forward weight their skis, points out Dr. Sol. He explains that evenly weighted skis provide the most stable support and control over direction. Drs. Maurer and Schneider say advanced skiers maintain forward pressure of the tibia on the boot cuff.