Objective To explore the relationship between the level of matrix metallo-proteinase(MMP)-2 ,MMP-3 ,MMP-9 and matrix metallo-proteinase inhibitor-1(TIMP-1) in the synovial fluid of the patients with knee joint osteoarthritis (OA) and the de-gree of articular cartilage injury and prognosis .Methods 52 patients(knee OA group) were given arthroscopic debridement com-bined with sodium hyaluronate ,diacerein .The levels of MMP-2 ,MMP-3 ,MMP-9 and TIMP-1 in synovial fluid were detected in 52 patients with knee OA and 10 normal controls(control group) by enzyme-linked immunosorbent assay .The degree of cartilage inju-ry was assessed with arthroscopy .Results The level of MMP-2 ,MMP-3 ,MMP-9 and TIMP-1 in knee OA group were significantly higher than those of the control group(all P<0 .01) .The levels of MMP-2 ,MMP-3 ,MMP-9 and TIMP-1 in the synovial fluid were positively correlated with the degree of articular cartilage injury ,and the levels of MMP-2 ,MMP-3 ,MMP-9 and TIMP-1 decreased with the improvement of the disease .Conclusion The measurement of MMP-2 ,MMP-3 ,MMP-9 and TIMP-1 have a certain signifi-cance to early diagnosis ,degree judgment and prognostic evaluation of knee OA .