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.

Orthoses that are designed to modify the structural and functional characteristics of the neuromusculoskeletal systems of the spine and skull; the device may be custom fabricated to meet the functional needs of the individual user or prefabricated to meet a particular set of functional requirements; the prefabricated devices may be adjustable to fit an individual user, or they may be ready-to-use so that adjustment is not possible or no adjustment is necessary for any user.

Articulating components of orthoses allow or control the motions of anatomical joints of the spine. Included are, e.g joints for spinal orthoses.