Association between body composition, knee synovial effusion, and serum glutamate in middle-aged women with knee osteoarthritis: a cross-sectional study

This cross-sectional study investigated the association between knee synovial effusion, body composition, and serum glutamate levels in middle-aged women with knee osteoarthritis. Female participants (n = 241) from a health promotion project were classified into control (n = 165), early (n = 34), and definitive (n = 42) knee osteoarthritis groups. Synovial effusion was assessed based on the ultrasonographic effusion area, body composition via bioelectrical impedance, and serum glutamate from fasting blood samples. Muscle mass was higher in the definitive group than in the control (p = 0.009). Fat mass increased from normal to definitive, showing a significant difference between the control and definitive groups (p = 0.047). The effusion area correlated with muscle mass (r = -0.122, p < 0.05) and glutamate levels (r = 0.154, p < 0.001). Logistic regression identified fat mass as an associated factor of early (OR = 1.089, p = 0.004) and definitive (odds ratio = 1.063, p = 0.005) knee osteoarthritis, suggesting a potential association between adiposity and knee osteoarthritis. A weak correlation was observed between serum glutamate and synovial effusion. These findings underscore the importance of body composition optimization as a potential approach in the context of knee osteoarthritis management.