Both the synovial score and the effusion-synovitis volume in the EKOA group were significantly higher than those in the normal group (p = 0.003 and p = 0.001, respectively) (Fig. 1).There was a weak positive correlation between serum MMP-3 concentration and effusion-synovitis volume (r = 0.176, p = 0.003) (Table 3). Here, MMP3 is linked to synovitis.