and pathologies associated with these limitations. These categories are presented not to suggest that these pathologies and impairments be studied exclusively but, rather, to prioritize the need for the development of knowledge related to significant functional limitations affecting human independence, autonomy, and productivity in society. The state of knowledge for selected pathologies and related impairments is reviewed to describe the gaps in knowledge that exist and promising areas in which knowledge can be developed through research from the perspective of rehabilitation science and engineering.

Knowledge in the realms of pathology and impairment comes from a variety of disciplines that partially overlap. Biology, engineering, and the physical, social, and behavioral sciences all contribute to rehabilitation science and engineering, in that those disciplines provide knowledge related to the altered cell and organ functions that may lead to disabling conditions. Rehabilitation science and engineering is unique in that it melds the knowledge from these otherwise distinct disciplines and creates a multidisciplinary structure that allows one to understand the nature of disability, that is, how potentially disabling conditions develop, progress, or reverse and the factors that mediate disabling or enabling processes. So, although an array of biological sciences offers knowledge of the normal molecular-cellular and organ-organ system level of performance, as well as of the molecular, cellular, and organ defects that lead to various pathological states and impaired organ system function, many of the factors that determine enabling and disabling processes and movement between the realms of pathology and impairment are related to disciplinary knowledge beyond that from the biological sciences. For example, replacement of organ function may entail an artificial organ (e.g., kidney dialysis machine, mechanical heart, or artificial hip) that emanates from a combination of medical and engineering research. Developments in engineering offer the hope of providing environments to assist with human functioning in the face of disability and impairment. Social sciences provide knowledge of the influence of personal lifestyle and societal conventions on enabling and disabling processes, even disability-related changes in performance at the molecular and cellular (pathology) and the organ (impairment) levels. The health professional disciplines support and stimulate the basic science research relevant to rehabilitation science and engineering and, most importantly, see that new knowledge from the basic sciences and rehabilitation science and engineering is translated into therapeutics and clinical care.