ABSTRACT
This chapter reviews the definition, nomenclature and ideal characteristics of orthoses. Orthotics is defined as the specialty relating to orthoses and their use. The word 'orthosis' seems to be derived from a combination of the words 'orthopaedic' and 'prosthesis'. Traditionally, orthoses have been named after a part of the body, a person, a place or an institution, but rarely after function. In the 1960s, the American Academy of Orthopaedic Surgeons (AAOS) set up a task force to suggest standard reproducible terminology for orthoses. Orthoses inevitably have to strike a balance between the often-conflicting requirements of function, cosmesis and acceptability. A basic understanding of biomechanics is essential when prescribing orthoses. Newton's third law of reaction, which states that for every reaction there is an equal and opposite reaction, is vital for comprehension of the principle of ground reaction force (GRF). Orthoses function by application of mechanical forces to the musculoskeletal system.
