One hundred thirty patients undergoing primary total knee arthroplasty (TKA) for knee osteoarthritis were randomized to receive surgery with a tourniquet (n=65) or without a tourniquet (n=65). The primary outcome was quadriceps thickness. Secondary outcomes included quadriceps stiffness, operation time, intraoperative blood loss, postoperative blood loss, total blood loss, transfusion rate, thigh circumference, pain scores (VAS), D-Dimer and CRP levels, knee function scores, patient satisfaction, and complications. Outcomes were assessed up to two years postoperatively. Overall, the results revealed that the tourniquet group had significantly less total blood loss and intraoperative blood loss but greater postoperative blood loss and a higher D-Dimer level on postoperative day 3. Other clinical parameters, including quadriceps thickness, stiffness, pain scores, function scores, and complications, showed no significant differences between groups. These findings suggest that tourniquet use effectively reduces intraoperative and total blood loss without worsening quadriceps injury or clinical outcomes, supporting its regular use in TKA.