One hundred patients scheduled for total knee arthroplasty under spinal anaesthesia and preoperative single-shot femoral nerve block were randomized to receive either continuous femoral nerve block with 0.125% bupivacaine for 48 hours after arrival to the postanaesthesia care unit, or to placebo saline. The purpose of this study was to evaluate the analgesic effect of continuous femoral nerve block as compared with placebo saline after total knee arthroplasty. Upon follow-up for 3 days postoperatively, no significant differences between groups were observed for pain scores, opioid use or the incidence of opioid-related side effects, incidence of motor blockade, or knee range of motion.