Muscle strength characteristics and central bone mineral density in women with recent onset rheumatoid arthritis compared with healthy controls

Abstract

Muscle strength and bone mineral density (BMD) at the lumbar spine (BMDspine) and femoral neck (BMDfem) were determined in 20 healthy women and in 20 women with recent onset rheumatoid arthritis (RA). The mean duration of articular symptoms of the patients was eleven months and none of them had used glucocorticoids or disease modifying antirheumatic drugs. BMDs were measured by dual x-ray absorptiometry (DXA). Knee extension, trunk extension, and flexion as well as grip strength were measured with David 200 and Digitest dynamometers. BMDspine (1.17 g/cm2 and 1.20 g/cm2) and BMDfem (0.98 g/cm2 and 0.96 g/cm2) between the women with early RA and healthy women did not differ. However, knee extension strength was 46%, grip strength 31%, trunk extension strength 14% and overall muscle strength index 29% lower in RA women (p < 0.020-0.001) than in healthy subjects. Femoral neck BMD correlated statistically significantly with knee extension strength and muscle strength index in both groups and with trunk extension and flexion strength as well as rapid force development in RA women. The data indicates that the loss of muscle strength is clearly visible during the first months of disease but the significant bone loss at central bone regions develops later.