ObjectiveThe aim of this study was to identify the influence of a tourniquet on the blood loss, transfusion requirement, swelling, pain, knee function, range of motion (ROM), operation time, bone cement mantle thickness, and complications in patients operated with total knee arthroplasty (TKA).MethodsTwo authors independently retrieved PubMed, Embase, and CENTRAL to identify eligible randomized controlled trials (RCTs) evaluating the effectiveness of a tourniquet in TKA. Fixed- (I2 < 50%) or random-effects (I2 > 50%) models were selected to perform meta-analysis according to the value of I2. Mean difference (MD) and risk ratio were selected as the effect sizes for continuous and dichotomous variables, respectively.ResultsA total of 29 RCTs, involving 2,512 operations (1,258 procedures with a tourniquet and 1,254 procedures without a tourniquet), were included, and 18 outcomes were compared. Tourniquet application could significantly decrease intraoperative blood loss (MD = −138.72 ml, p < 0.001), shorten operation duration (MD = −1.77 min, p < 0.001), and increase cement mantle thickness (MD = 0.17 mm, p < 0.001). However, it was significantly associated with increased postoperative pain intensity, decreased full ROM/flexion ROM/extension ROM, poorer knee function, increased knee swelling, and increased length of hospital stay (LOS) at several follow-up points (p < 0.050). No significant difference was found for postoperative draining volume, total blood loss, transfusion rate, change of Hb level, and risks of deep venous thrombosis and all complications.ConclusionsTourniquet application could only decrease the intraoperative blood loss but has no effectiveness on the total blood loss and transfusion requirement. On the contrary, it has a reverse effect on the pain score, knee function, ROM, swelling, and LOS.