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Disability Evaluation – Distinguishing Disability and Impairment

It is now widely recognized that work, or vocational, disability is a complex construct that must be assessed from a biopsychosocial (rather than biomedical) perspective that considers both medical and non-medical factors.  Despite this recognition, an individual’s degree of vocational disability, and thus his or her return-to-work potential, is often equated to the severity of his or her medical impairment. Impairment has been defined as a significant deviation, loss or loss of use of any body structure or body function in an individual with a health condition, disorder or disease.  Disability, on the other hand, has been defined as an inability to perform or a limitation in performing socially-defined roles and tasks (e.g. working and earning money) expected of an individual within a sociocultural and physical environment.  A key distinction between impairment and disability is thus that impairment lies entirely within a person whereas disability is a function of the interaction between a person (e.g. worker) and his or her environment (e.g. workplace).  Consequently, an individual’s medical impairment is usually more easily identifiable and measurable than his or her disability.  

While using medical impairment ratings as proxy measures of vocational disability may result in a reliable, or consistent, disability estimation methodology, it will often lead to invalid estimates of an individual’s true degree of disability.  This is because medical impairment is a necessary but insufficient predictor of vocational disability, or return-to-work potential. The faulty logic of automatically equating impairment with disability can be demonstrated with an example of how two individuals with the same type of injury and severity of impairment can have a considerably different level of disability.  For instance, consider a 35-year old with a doctorate degree who works as a clinical psychologist and a 55-year old high school dropout who works as a structural-steel worker. If both individuals sustained similar traumatic injuries to one of their lower extremities and that resulted in a below-the-knee amputation at the same level, they would have an identical impairment rating.  However, assuming both individuals are permanently limited to sedentary exertion and require ambulatory assistance, the clinical psychologist would still likely be able to return to his or her pre-injury employment whereas the structural-steel worker would not. In addition, unlike the clinical psychologist, the structural-steel worker would be much less likely to be able to return to his or her pre-injury wage level. Thus, taking into account non-medical factors such as age, education and work history, the structural-steel worker’s degree of disability (i.e. as measured by wage loss) is likely to be much higher than that of the clinical psychologist.  

This example clearly illustrates the need for a qualified and competent vocational rehabilitation professional to evaluate injury and disability claims (e.g. personal injury claims; workers’ compensation claims; federal/VA/long-term disability claims) to help determine the length (temporary or permanent) and severity (partial or total) of vocational disability, if any, that an individual has sustained.  With this in mind, when conducting independent evaluations of an evaluee’s employment and/or earning potential, Dr. Hankins considers a multitude of personal and environmental factors to assess the likely impact of any permanent functional limitations and restrictions on the individual’s residual ability to work and earn money. Through this detailed process, conclusions can be reached about an evaluee’s degree of disability, and thus about his or her residual employment and/or earning potential, that can be expressed within a reasonable degree of vocational and rehabilitation economic certainty.