The way the body moves is dependent on the sub-talar joint, which is a tri-planar joint near the ankle. It serves to PRONATE and SUPINATE the foot. Pronation helps the weight-bearing joints (feet, ankles, knees, hips, lower back) to absorb shock while supination aids in support and stability. To have an efficient gait cycle, small amounts of pronation and supination are needed. Most commonly, people tend to have feet that excessively pronate but there is a small percentage that excessively supinate - and an even smaller percentage of the population that have feet that work perfectly!!  Orthotics can work really well to control the degree of movement in the sub-talar joint which helps the body move more efficiently.