Forty-eight patients were divided into 2 groups to compare the use of a 0.3mg dose of buprenorphine as an adjuvant in femoral nerve block to the sole use of femoral nerve block with a solution of 0.25% bupivacaine and adrenaline following total knee arthroplasty. The purpose of the study was to determine whether buprenorphine, a long-lasting opioid, would be able to improve the quality and duration of the administered femoral nerve block. A numerical rating scale (NRS) was the primary outcome of interest, and it was measured at 12, 24, 36, 48, 60, and 72 hours following the procedure. Patients who received the additional dose of buprenorphine indicated a lower level of pain at postoperative 12 hours than patients in the control group.