Ski boots are designed to restrict foot and ankle motion, so that muscle power can be transferred to the ski rather than lost to joint motion. This restriction on feet evolved to move can cause achy feet and legs and can restrict vein circulation. Knees are subjected to higher forces compared to walking. HealthyStep advises that ski boots are professionally fitted and that the foot is supported gently from below with either mild foot cradling Fallen Arch Insole – arch angel) or with stronger support for weaker feet (X-Line TPD50).