We assessed the effectiveness of intra-articular solutions of morphine, bupivacaine with adrenaline and a combination of both, compared with placebo in facilitating mobilisation and reducing postoperative pain and analgesic requirements for 24 h after operation. Forty patients undergoing arthroscopic knee surgery were studied in a double-blind, randomised, controlled trial. All treatments proved more effective than placebo in facilitating earlier mobilisation and in decreasing postoperative pain as measured by visual analogue scale. Morphine alone provided the best analgesia and significantly decreased analgesic consumption for 24 h after surgery. We conclude that 1 mg of intra-articular morphine provides effective pain relief following arthroscopic knee surgery and that the addition of bupivacaine is of no benefit.