The objective of this prospective, randomized, double-blind study was to determine if preoperative administration of a femoral nerve block reduces the amount of morphine needed for postoperative analgesia after total knee arthroplasty (TKA). Forty-two patients undergoing TKA were randomly assigned to receive either a femoral nerve block (0.50% bupivacaine hydrochloride with epinephrine 1:200,000) or matching placebo. Results showed postoperative morphine use was significantly lower in patients who received the nerve block (25.5 vs 37.5 mg, P = .016); however, the 2 groups had similar pain scores and rehabilitative outcomes. In general, a preoperative femoral nerve block is a safe and effective adjunct for decreasing morphine use for post-TKA analgesia.