Absolute reduction in lower limb lean body mass in Japanese women with knee osteoarthritis

Background: Knee osteoarthritis (OA) is a significant contributor to disability, and obesity is one of the most modifiable risk factors. The association between knee OA and obesity has been reported to relate to quadriceps strength. To begin to examine this hypothesis, independent measures of quadriceps lean mass are needed. Objective: The objective of this study was to characterize the absolute lower limb lean body mass in women with knee OA. Methods: Japanese women, aged 45 and over, who presented to a community orthopedics clinic, were categorized as 1) those with no knee pain, presenting with fracture, sprain, or back pain (n = 604); and 2) those presenting with knee pain meeting clinical and radiographic criteria for knee OA (n = 341). Segmental lower limb lean body mass (L-LBM) was measured with multifrequency bioelectrical impedance analysis and subjects were stratified by body mass index (BMI) by Western Pacific Region World Health Organization weight categories. Results: Control and knee OA groups were comparable with respect to age and BMI. Despite an increase in L-LBM with increasing BMI, there was a statistically significant reduction in L-LBM in knee OA subjects in comparison with control subjects in matched normal weight, overweight, and obese strata (11. 1, 12.4, and 13.1 kg in the nonknee OA compared with 10.5, 10.6, and 11.6 kg in the knee OA group). Conclusions: A reduction in absolute L-LBM is observed in older Japanese women with knee OA in comparison with control subjects. Longitudinal studies are warranted in which L-LBM can be prospectively evaluated in a cohort followed for incident knee OA to better characterize the temporal relationship with L-LBM decline. Clinicians should consider this reduction in L-LBM in women with knee OA to recommend therapy aimed at reducing risk for atrophy and disability.