Abstract: Objective To investigate and analyze the correlation between the level of complement C3 in knee synovial fluid and knee arthritis. Methods From July 2018 to May 2021 in the hospital of traditional Chinese medicine of knee arthritis in 126 patients as 126 cases, in the same period, 126 cases of healthy physical examination of knee arthritis were selected as the control group, the level of knee synovial complement C3 and other serological indicators, the KL grade score of the patients with knee arthritis was evaluated, and the correlation between the KL grade score and complement C3 levels were analyzed. Results The level of complement C3 in the synovial fluid of the knee arthritis group were higher than that of the control group (P<0.05). The serum levels of antinuclear antibody (ANA), C4, cyclic citrullinated peptide (CCP) in the knee arthritis group were higher than those in the control group (P<0.05), and the immunoglobulin G levels compared were no statistically significant difference between the two groups (P>0.05). In the knee arthritis group, the KL grading score were (6.33±0.52) points. Pearson correlation analysis showed that the KL grading score were positively correlated with knee synovial fluid complement C3 and serum ANA, C4, CCP(P<0.05); in the knee arthritis group, unconditioned logistic regression analysis showed that knee synovial fluid complement C3, antinuclear antibodies, serum C4, and cyclocitrulline peptides served as important risk factors affecting the KL grade score (P<0.05). Conclusion Patients with knee arthritis are mostly accompanied by high expression of complement C3 in the synovial fluid of the knee joint, which are correlated with the patient's KL grading score and are also important factors affecting the KL grading score.

Key words: knee arthritis, joint synovial fluid, complement C3, KL grade score, antinuclear antibody, correlation, cyclic citrullinated peptide