This randomised, double-blind study compared the analgesic properties of intra-articular injection of morphine and bupivacaine during therapeutic arthroscopic knee surgery. Forty male patients were randomly divided into 4 groups of 10 patients each. Group A received intra-articular injection of 1 mg morphine sulphate in 20 ml saline, Group B received 20 ml of 0.25% bupivacaine while Group C received 1 mg morphine sulphate in 20 ml of 0.25% bupivacaine injected intra-articularly. Group D did not receive intra-articular injection and acted as control. Post-operative pain was assessed by visual analogue score. The morphine group had significantly lower pain score compared to the control group from 4 hours onwards throughout the 24-hour study period (p < 0.05 at 4 hours and p < 0.001 at 24 hours). The bupivacaine group had lower pain score than the control group during the first 4 hours (p < 0.001 at 1 hour and p < 0.05 at 2 hours). At 4 hours, it showed similar analgesic efficacy as morphine. There was no significant analgesic effect at the end of the study period. The combination of the two drugs resulted in satisfactory analgesia throughout the entire study period (p < 0.001 at 1, 2 and 24 hours and p < 0.05 at 4 hours) and appeared to be a simple, safe and effective analgesic technique for patients who underwent therapeutic arthroscopic knee surgery.