orthoses from Greek ortho , to straighten. Custom-designed external devices used to control or counteract the effect of an actual or developing deformity. They include braces, splints, etc. In sport the term is most commonly used to describe foot-supporting insoles used to correct structural imbalance which may result in discomfort in the back, hips, knees or feet. Orthoses decrease the risk of further injury and make movement of the foot more efficient. orthotics the study and manufacture of orthoses.