In total knee arthroplasty (TKA), the use of a tourniquet and controlled hypotension is common. However, ischemia-reperfusion injury induced by the tourniquet and inappropriate controlled hypotension can lead to cardiac and cerebral damage in patients. Consequently, maintaining hemodynamic stability, ensuring adequate cerebral perfusion, and achieving controlled blood pressure during the perioperative period are critical factors influencing patient outcomes. Postoperatively, patients typically experience moderate to severe pain. Severe postoperative pain can result in prolonged hospital stays, increased readmission rates, elevated opioid consumption, and associated nausea and vomiting. Therefore, exploring effective multimodal postoperative pain management strategies is essential. Nalbuphine, an opioid analgesic acting as a full kappa-receptor agonist and a partial mu-receptor antagonist, is considered to provide analgesic efficacy equivalent to morphine while potentially offering advantages in maintaining hemodynamic stability. This study aims to investigate the effects of administering equivalent doses of nalbuphine at different perioperative time points on analgesia and hemodynamics in elderly patients undergoing knee arthroplasty.