Objective:To investigate the expression and significance of MT1-MMP in the synovium of knee joint of patients with osteoarthritis. Methods:We detected the expression of MT1-MMP protein in 80 cases of osteoarthritis by using.immunohistochemically and Western blot. Results:The expression of MT1-MMP protein in the synovium of knee joint of patients with osteoarthritis was markedly higher that in the normal synovium (χ2=29.46,P < 0.01), and the MT1-MMP protein was mainly located in the cytoplasm; The results of Western blot showed that the expression of MT1-MMP protein in the synovium of knee joint of patients with osteoarthritis(1.042 ± 0.219) was significantly higher than that in the non-osteoarthritis (0.256 ± 0.050,F = 12.838,P = 0.001). Conclusion:There is a close relation between the expression of MT1-MMP protein and OA, it may be the marker of diagnosis and the judgment of osteoarthritis.