The levels of adiponectin, vascular endothelial growth factor (VEGF), matrix metalloproteinase (MMP)-1, and MMP-13 in the joint fluid of patients with rheumatoid arthritis (RA) or osteoarthritis (OA). The joint fluid levels of (a) adiponectin and (c) MMP-1 were significantly higher in RA patients than in OA patients, whereas (b) VEGF and (d) MMP-13 were not statistically different between RA and OA patients. Joint fluid samples from 30 patients in each group were used for the analysis. Values are expressed as mean ± standard error of the mean. * P < 0.05, *** P < 0.001 versus OA patient group.