To examine relationships of bone quality as assessed by quantitative ultrasound (QUS) and bone mineral density (BMD, g/cm(2)) with quadriceps strength (QS) in women with rheumatoid arthritis (RA).
Sixty seven women with RA according to the 1987 American College of Rheumatology (ACR) criteria were examined. Mean (SD) age was 62 (13) years, mean disease duration 15 years. Most were or had been receiving glucocorticoid treatment. Calcaneal bone quality expressed as speed of sound (SOS, m/s), broadband ultrasound attenuation (BUA, dB/MHz), and stiffness was measured by QUS. BMD of the femoral neck, spine, and distal forearm was measured by dual energy x ray absorptiometry (DXA). Maximal voluntary isokinetic quadriceps strength (Nm) was assessed by isokinetic dynamometry. Pain was recorded on a visual analogue scale (VAS), disability was scored by the Stanford Health Assessment Questionnaire (HAQ), and the degree of physical impairment was expressed by the Steinbrocker index (SI).
In multiple regression analyses, QS predicted SOS, BUA, and stiffness (r(partial) ranging from 0.36 to 0.45, p<0.005) and femoral neck BMD (r(partial)=0.30, p<0.05) independently of age, height, weight, disease duration, HAQ, VAS, SI, and cumulative steroid dose. BMD of the spine and distal forearm was not associated with QS. After adjustment for covariates, women with subnormal BMD of the femoral neck (T score <-1), had a 20% lower QS than those with normal BMD (p<0.0001).
Calcaneal bone quality and femoral neck BMD were associated with QS in women with RA. This finding indicates that physical activity including muscle strengthening exercises may play a part in the prevention of bone loss in these patients.