Muscle strength, muscle balance, physical function and plasma interleukin-6 (IL-6) levels in elderly women with knee osteoarthritis (OA)

An increased circulating level of inflammatory cytokines has been associated with sarcopenia, functional disability, chronic diseases, and mortality in the elderly. Osteoarthritis (OA) is a disease common to this population, the seriousness of articular degeneration has been associated to the increase in some cytokines, IL-6 among them. The aim of the present study was to correlate IL-6 plasma levels with muscle strength, endurance, muscle balance hamstring/quadriceps (H/Q) and physical function in 80 elderly women (71.2 ± 5.3) with knee OA. IL-6 was measured using enzyme-linked immunosorbent assay (ELISA). Quadriceps and hamstring muscle strength, endurance and hamstring-quadriceps muscle balance were assessed using a Biodex system 3 pro^® isokinetic dynamometer. Physical function was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Spearman's correlation coefficient was used to explore the relationship between the outcomes at the significance level of α = 0.05. IL-6 was inversely correlated to the endurance of the hamstring muscles (r = −0.232; p = 0.03) and muscle balance (H/Q) on the lower right side at 180°/s (r = −0.254; p = 0.023). No significant correlation between IL-6, muscle strength and physical function was found. Our results show that elevated levels of IL-6 may possibly contribute to the reduction of the endurance of hamstring muscles and H/Q muscle balance in the elderly studied.