INTRODUCTION: Total knee arthroplasty (TKA) is a commonly performed surgical procedure for the treatment of advanced-stage knee osteoarthritis. This study aims to compare perioperative blood loss between tourniquet-assisted and tourniquet-free TKA using the reference change value (RCV), a personalized analytical tool that accounts for both biological and analytical variability. MATERIALS AND METHODS: A retrospective analysis was conducted on 137 patients (tourniquet group (n = 68) and non-tourniquet group (n = 69) who underwent primary TKA. Hematological parameters-including red blood cell count (RBC), hemoglobin (HGB), and hematocrit (HCT)-were evaluated preoperatively, on the day of surgery, and on postoperative day one. Blood loss was assessed using both conventional statistical methods and RCV-based analysis. RESULTS: No statistically significant differences were observed between the two groups in terms of age and gender (p > 0.05). Although preoperative hemoglobin levels were significantly different between groups (p < 0.05), there were no significant intergroup differences in pre- or postoperative RBC and HCT values. Traditional statistical analysis showed no significant difference in blood loss (p > 0.05). However, RCV analysis revealed that while bleeding had stabilized by the first postoperative day in the non-tourniquet group, it remained significantly elevated in the tourniquet group. CONCLUSIONS: The findings suggest that RCV offers a more individualized and sensitive approach to assessing perioperative blood loss in TKA. Although conventional methods did not demonstrate significant differences, RCV analysis indicated a more rapid hemostatic response in the non-tourniquet group. Incorporating RCV into routine clinical practice may enhance patient-specific blood management and support earlier postoperative decision making.