MMP13 and arthritic joint disease: Clinical severity of arthritis was higher in WT mice compared with MMP-13–/– mice (day 8 (mean ± standard deviation): inflammation score, 6 ± 0.5 in WT mice and 1.8 ± 0.5 in MMP-13–/– mice, P <0.05; destruction score, 1.5 ± 0.5 in WT mice and 0.6 ± 0.5 in MMP-13–/– mice, P <0.0043) (Figure 3).