APOA1 and rheumatoid arthritis: Unexpectedly, ApoA1 levels were highly correlated to total cholesterol (r = 0.72; P<0.0001) and LDL levels (r = 0.64, P<0.0001) inside the OA joint cavity but not inside their corresponding OA serum [r = 0.11 (P = 0.56); r = -0.08 (P = 0.68)] or inside RA synovial fluid [r = 0.33 (P = 0.14); r = -0.33 (P = 0.9)] (Table 3).