Objective To explore the relationships between the levels of synovial fluid and serum interleukin-1(IL-1)and tumor necrosis factor alpha(TNF-α)and severity of knee osteoarthritis (OA). Methods 50 patients with unilateral OA(18 cases in early stage,15 cases in middle stage,and 17 cases in terminal stage)were included in the study.15 healthy volunteers were examined as the control group.Synovial fluid and serum of all patients and volunteers were collected for measurement of IL-1 and TNF-α. Results The IL-1 and TNF-α levels of synovial fluids and serum in OA group were significantly higher than those of the control group(P <0.01).With the progress of OA,the IL-1 and TNF-α levels were increased significantly(P <0.01).IL-1 level in synovial fluid and serum of OA group was correlated positively with TNF-α level(P <0.01). Conclusion IL-1 and TNF-α were related to OA patients with immune inflammation,and their levels could reflect changes in disease activity.The increasing IL-1 and TNF-α levels in synovial fluids and serum were positively correlated with the progress of OA.Therefore,combined detection of these two indexes could be useful for determining the pathogenetic condition of KOA.