Orthoses are externally applied devices used to modify the structural and functional characteristics of the neuromusculoskeletal systems; prostheses are externally applied devices used to replace, wholly or in part, an absent or deficient body segment. Included are, e.g. body-powered and externally powered external orthoses, prostheses, orthopaedic footwear. Excluded are endo-prostheses, which are not part of this document.

A collection of compatible components that can be integrated to produce a range of different lower limb prostheses. Included are, e.g. cosmetic lower limb prostheses.

Functional components of lower limb prostheses that substitute for some of the dynamic and sensory attributes of the normal limb and that substitute for some of the functions of the normal ankle and foot by means of controlled motions. Included are, e.g. separate ankle units, foot units.