Eighty patients with osteoarthritis undergoing primary unilateral total knee arthroplasty were randomized to receive either a combination of celecoxib, pregabalin, and acetaminophen (n=40) or celecoxib, pregabalin, and placebo (n=40) two hours prior to surgery. The primary outcome was total morphine consumption postoperatively. Secondary outcomes included time to initial rescue analgesia, pain scores via VAS, functional recovery (knee range of motion and ambulation distance), hospitalization duration, and postoperative complications. Outcomes were assessed up to 48 hours postoperatively. Overall, the results of the study revealed no significant differences between groups for any outcomes, including morphine use (P=0.242), pain scores, or functional recovery. These findings suggest that adding acetaminophen to preemptive multimodal analgesia does not improve postoperative pain control or reduce opioid use after total knee arthroplasty.