The association between pain, impairment and disability is frequently observed in clinical practice but the relationship is not as straight-forward as just one to one; for example some patients may have severe pain but little impairment. Consequently, a group of investigators from University of Bergen in Norway set about trying to establish a more concrete idea of the interaction between these relative dimensions to quality of life.

They recruited 223 patients with musculoskeletal pain who had been sick-listed for an average of 3.3 consecutive months, onto the trial. Participants (65% women) had an average age of 43 years. Each patient was assessed on three separate occasions to measure pain intensity, disability and physical impairment. A combined score was then calculated to establish the relative degree of each problem and allow relationships between the dimensions to be quantified. The first examination took place before the start of a four week intensive multidisciplinary treatment program. The second exam was carried out on completion of the program (n=213) and the final exam was performed six months later (n=193). Pain intensity was measured using a visual analogue scale (VAS), disability was recorded using the established Disability Rating Index (DRI) self assessment questionnaire and impairment was judged via 16 validated movement tests from the Global Physiotherapy Examination.

The strongest relationship was demonstrated between pain intensity and disability with r equalling .50, .69 and .78 for each exam, respectively. This closely matches clinical observation where degree of pain is frequently seen to restrict a patient\'s ability to perform certain tasks. However, measurements before the trial showed no significant relationship between pain intensity and impairment (r=13) and only a small association post-test and at 6 months (r=.29 and .42 respectively). Similarly the overlap between loss of specific movements (impairment) and disability was comparatively small although still statistically significant (r=.27, .30, .34).

Overall, the investigators highlight the direct and strong relationship observed between pain and disability but are quick to point out that each dimension was demonstrated to influence the other to some significant degree and so clinically, none should be considered in isolation.

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