【Abstract】 Objective To explore the correlation between expression levels of serum interleukin-17 (IL-17), tumor necrosis factor-α (TNF-α), transforming growth factor-β1 (TGF-β1) and tissue inhibitor of metalloproteinase-1 (TIMP-1) and disease severity of elderly knee osteoarthritis (KOA). Methods The clinical data of 148 elderly KOA patients admitted between January 2019 and December 2019 were retrospectively analyzed. All patients underwent X-ray examination and were given KL (kellgren Lawrence) classification. According to the classification results, the patients were divided into mildtomoderate group and severe group. The levels of IL-17, TNF-α, TGF-β1 and TIMP-1 were compared among patients with different disease severity. Spearman method was used to analyze the relationship between laboratory indexes levels and KL classification, and ROC curve was drawn to evaluate the diagnostic efficacy of above indexes on severe elderly KOA. Results There were no significant differences in the age, gender and body mass between KOA patients in mildtomoderate group and severe group (P＞0.05). The levels of IL-17, TNF-α in mildtomoderate group were lower than those in severe group (P＜0.05) while the TGF-β1, TIMP-1 was higher than that in severe group (P＜0.05). Spearman correlation analysis showed that KL classification was positively correlated with IL-17, TNF-α(P＜0.05), and was negatively correlated with TGF-β1,TIMP-1 (P＜0.05). ROC curve showed that IL-17, TNF-α, TGF-β1 and TIMP-1 could diagnose severe KOA (P＜0.05), and the AUC of TGF-β1 was the highest. Conclusion The expression levels of serum IL-17, TNF-α, TGF-β1 and TIMP-1 have different degrees of correlation with disease severity of elderly KOA patients, and can be used as auxiliary indicators for clinical disease evaluation.