Twenty-eight days after induction of collagen-induced arthritis, male Mmp12–/– B10.RIII mice (n = 20) exhibited more severe arthritis (Fig. 5a, b), with increased ankle width and histopathological scores compared with male Mmp12+/+ B10.RIII mice (n = 18). This evidence concerns the gene MMP12 and arthritic joint disease.