OBJECTIVES Although muscle mass has been shown to be positively related with bone mineral density (BMD), there are only a few studies that investigated the association between muscle strength or muscle quality and BMD. We investigated the effects of muscle strength and muscle fat infiltration, as a measure of muscle quality, adjusted for muscle mass on femoral neck BMD in Korean elderly cohort.

METHODS We recruited 242 men and 231 women aged over 65 years who participated in the Korean Longitudinal Study on Health and Ageing. Leg muscle mass and femoral neck BMD were measured by dual-energy X-ray absorptiometry. Isokinetic strength of knee extensors was measured as a peak torque value by an isokinetic device. Computed tomography scan of the mid-thigh measured the mean Hounsfield unit (HU) of the lean tissue. Low bone density was defined as femoral neck T-score ≤-2·0.

RESULTS Leg muscle mass, knee extensor strength and thigh muscle HU values were significantly positively correlated with femoral neck BMD in both men and women. However, muscle strength was not a significant determinant for the presence of low bone mass after adjusting for muscle mass in multiple logistic regression analyses. Notably, thigh muscle HU values were strong and independent determinant for the risk of low bone density.

CONCLUSION Decreased thigh muscle HU values, a measure of fatty infiltration of muscle, were independently associated with increased risk of low bone density in the elderly population.