ISOMETRIC MUSCLE STRENGTH IS AN INDICATOR OF SELF-REPORTED PHYSICAL FUNCTIONAL DISABILITY IN PATIENTS WITH RHEUMATOID-ARTHRITIS

The objective of our study was to examine (1) whether isometric muscle strength contributes to the explanation of the physical functional di sability of a rheumatoid arthritis (RA) patient population after accou nting for other disease parameters and demographic variables and (2) w hether change in isometric muscle strength is an indicator of change i n physical functional disability. Sixty-five consecutive patients fulf illing the American Rheumatism Association 1987 revised criteria for R A were included in the study. Isometric muscle strength was measured w ith a validated Muscle Strength Index (MSI) calculated as the mean sco re of standardized isometric extension and flexion strength of the kne e and elbow joints. Physical functional disability was measured with t he physical dimension of the Health Assessment Questionnaire (HAQ). Fo r 56 patients, we could obtain I yr follow-up data. Cross-sectionally, there was a significant correlation (r = -0.51, P < 0.01) between the MSI and the HAQ. Muscle strength remained a significant determinant o f the HAQ in multivariate analysis accounting for disease and demograp hic variables. Longitudinally, change in MSI explained additional vari ance of change in HAQ after accounting for change in pain, the most im portant correlate of change in HAQ.