This document defines orthotics as external devices that apply forces to the body to control motion or maintain proper positioning. It classifies orthotics by region of the body and function. The principles of orthotics include using forces like rigidity or springs to limit or assist movement according to Jordan's three point system. Orthotics are made of materials like plastic, metal, or leather and are used temporarily or permanently to relieve pain, correct deformities, protect injuries, and improve function. Contraindications include infections and devices that limit normal motion or interfere with clothing. Disadvantages can include skin problems, weakness, increased adjacent joint motion, and dependence.