We have investigated the value of a 3-in-1 nerve block, followed by a continuous low-dose infusion of bupivacaine into the femoral nerve sheath for postoperative analgesia after total knee replacement. Thirty-seven patients were randomly allocated to either a control group or a study group. The study group had a catheter placed in the ipsilateral femoral nerve sheath. A 3-in-1 nerve block was then performed in the study group with injection of 30 mL of 0.25% bupivacaine through the catheter. This was followed by a continuous infusion of 0.125% bupivacaine at 6 mL/h. The study group had significantly lower pain scores 4 and 24 h postoperatively (P less than 0.01) and required less postoperative opioid analgesic medication (P less than 0.01) than the control group. The authors conclude that a continuous low-dose infusion into the femoral nerve sheath results in better pain relief than conventional intramuscularly administered narcotics after total knee arthroplasty.