The relationship between impairment and disability in arthritis: an application of the theory of generalized linear models to the ICIDH.

We investigated the relationship between impairment, as represented by limitation in range of movement and pain in the knee joint, and disability as measured by a series of activities of daily living in 123 patients with either rheumatoid arthritis or osteoarthrosis. A log-linear modelling technique found there was a positive association between functional limitation, as measured by reduction in angle of flexion, and disability. However, there was only a marginal relationship between pain in the knee joint and disability, and no association between pain and range of movement, which suggests that conventional beliefs that pain is a key factor in assessing health outcomes may need to be reassessed.