Abstract:[Objective] To investigate the effect of esketamine on tourniquet injury in knee arthroplasty. [Methods] A total of 106 pa- tients who were undergoing knee arthroplasty under general anesthesia were included in the study. They were randomly divided into two groups, 53 patients received esketamine (the drug group), while other 53 patients not received esketamine (the non-drug group). The clinical and laboratory data of the two groups were compared. [Results] All patients in both groups were successfully operated on. The drug group had significantly lower mean artery pressure (MAP) than the non-drug group 60 min after torniquet applied [(109.7±8.3) mmHg vs (115.7± 9.5) mmHg, P<0.001] and 10 min after torniquet released [(102.6±7.4) mmHg vs (99.3±6.9) mmHg, P=0.019]. At the corresponding time points, the drug group got significantly lower NRS score for pain than the non-drug group (P<0.05). In addition, the drug group was mea- sured significantly greater femoral circumference than the non-drug group 7 days after operation [(42.7±5.4) cm vs (40.4±5.1) cm, P=0.026]. Regardless of insignificant difference in the incidence of nausea, vomiting and agitation between the two groups (P>0.05), the drug group had significantly lower incidence of postoperative delirium than the non-drug group (1.9% vs 15.1%, P=0.031). In terms of laboratory test, al- though there were no statistically significant differences in IL-6, LA and MDA levels between the two groups before operation (P>0.05). the drug group was tested significantly lower IL-6 [(407.3±26.7) pg/ml vs (432.5±28.7) pg/ml, P<0.001], LA [(0.8±0.2) mmol/L vs (1.0±0.2) mmol/L, P<0.001], and MDA [(4.4±0.6) μmol/L vs (4.8±0.6) μmol/L, P<0.001] than the non-drug group 10 min after torniquet released. [Conclusion] Esketamine does inhibit tourniquet hypertension, relieve tourniquet pain and prevent quadriceps atrophy in knee arthroplasty in this study.