deed, disfiguring dermatological impairments may cause societal disability but engender no functional limitations.
The term impairment, for example, describes abnormalities in specific organs or organ systems (see Chapter 4). Pain* and decrements in strength, range of motion, balance, and endurance are examples of impairments. Functional limitations are restrictions or lack of abilities in performance of the whole organism or individual, assessed in a manner to eliminate external environmental barriers to performance. An individual's gait and other locomotor activities as assessed in a gait laboratory are examples of functional limitations measures. As such, functional limitations reflect an attribute of the capacity of an individual. In this report functional limitation is used as defined and discussed by Nagi (1965) and further developed in Disability in America (Institute of Medicine, 1991).
Disability, in contrast to functional limitation, is a relational concept that describes any restriction or lack of ability to perform an activity in the manner or within the range considered normal for a human being. As a relational concept, disability reflects the individual's capacity to perform a task or activity necessary to achieve a role such as homemaker, worker, parent, or spouse, as well as the environmental conditions in which they are to be performed. These activities can be organized and assessed across different spheres of life. Thus, a subject's report of self-care performance (as reflected in the Sickness Impact Profile, Functional Independence Measure [FIM], Barthel, and other traditional activities of daily living [ADL] measures) is an activity, and measures of such are indicators of disability.
The link between changes in impairment and changes in functional limitation has long been assumed, but it has rarely been documented scientifically. New impairments have been shown to engender locomotor compensatory mechanisms; to date, however, no data are available to link impairments to such compensatory mechanisms in individuals with specific functional limitations or disabilities. Until this link is established, it will be impossible to discern compensatory mechanisms such as Trendelenburg gait resulting from primary disabling and functionally limiting mechanisms such as hip abductor muscle weakness or range of motion limitation.
Most often, pain is considered an impairment, a result of a pathology or impairment, and a cause for functional limitation. Chronic pain, pain that persists for 3 months or longer, has implications across the enabling-disabling process, with most significant impact at the level of disability and quality of life. Thus, pain may be identified at multiple areas of the model and may be modified through a variety of interventions.