Muscle strength, mass, and quality in older men and women with knee osteoarthritis

Objective To examine the relationship between knee osteoarthritis (OA) and muscle parameters in a biracial cohort of older adults. Methods. Participants in the Health, Aging and Body Composition Study (n = 858) were included in this cross-sectional analysis. Computed tomography was used to measure muscle area, and quadriceps strength was measured isokinetically. Muscle quality (specific torque) was defined as strength per unit of muscle area for both the entire thigh and quadriceps. Knee OA was assessed based on radiographic features and knee pain. We compared muscle parameters between those with and without radiographic knee OA (+RKOA group and -RKOA group, respectively) and among 4 groups defined by +RKOA and -RKOA with and without pain. Results. The mean +/- SD age was 73.5 +/- 2.9 years and the mean +/- SD body mass index (BMI) was 27.9 +/- 4.8 kg/m(2). Fifty-eight percent of participants were women and 44% were African American. Compared to the +RKOA participants, -RKOA participants had a higher BMI (30.2 versus 26.8 kg/m(2)), larger thigh muscles (117.9 versus 108.9 cm(2)), and a greater amount of intermuscular fat (12.5 versus 9.9 cm(2); all P < 0.0001). In adjusted models, the +RKOA participants had significantly lower specific torque (P < 0.001), indicating poorer muscle quality, than +RKOA participants, but there was no difference between groups in quadriceps specific torque. The +RKOA without pain (P < 0.05) and the +RKOA with pain (P < 0.001) participants had lower specific torque compared to the -RKOA without pain group. There were no significant differences in quadriceps specific torque among groups. Conclusion. Muscle quality was significantly poorer in participants with RKOA regardless of pain status. Future studies should address how lifestyle interventions might affect muscle quality and progression of knee OA.