To determine the role of MMP-13 during the development of K/BxN sera-induced arthritis, MMP-13–/– mice and the WT control mice were injected intraperitoneally with 200 μl arthritogenic K/BxN serum and indicative parameters of arthritis were compared in WT mice and mutant mice over time. The gene discussed is MMP13; the disease is arthritic joint disease.