In brief:Orthoses can be used inside downhill ski boots to aid in parallel skiing. Small degrees of imbalance become significant when they affect the skier's posture and ability to turn. The author explains how orthoses, cants between the boot and the ski, and posts correct biomechanical deformities including tibial varus and valgus, subtalar varus, forefoot varus and valgus, and leg-length discrepancies. He advises skiers whose feet hurt to find a good podiatrist and a reliable ski boot fitter.