Intravenous patient controlled analgesia may not provide complete postoperative analgesia following total knee arthroplasty. The present study was to evaluate whether the addition of local, intra-articular ropivacaine improves the quality of the analgesia after total knee arthroplasty.

In the prospective, double-blind trial, 17 patients undergoing total knee arthroplasty of both knees with a standard general anesthetic technique had a infusion catheter placed at each knee joint at the end of surgery. The first knee joints were randomly assigned to receive a bolus of 20 ml 0.75% ropivacaine or saline followed by continuous infusion at 2 ml/h for 48 hours. The later knee joints received saline or ropivacaine that was not administered in the first knee joints in same manner. All patients received IV PCA. The difference in pain for each knee was assessed before surgery and at 2, 4, 6, 12, 24, 36 and 48 hours postoperatively. The use of a visual analogue scale (VAS) for each knee was also assessed at 2, 4, 6, 12, 24, 36 and 48 hours postoperatively.

The difference in pain between each knee significantly increased at 4, 6, 12, 24, 36, 48 hours. However, the VAS in the ropivacaine-infused knee was significantly lower than that in the saline-infused knee at 12 and 24 hours.

These results suggest that an intra-articular infusion of a bolus of 20 ml followed by continuous infusion at 2 ml/h with 0.75% ropivacaine after total knee arthroplasty has only a marginal analgesic effect.