200 patients underwent either total hip replacement (THR) or total knee replacement (TKR). They were then randomised into two groups to either receive usual care and a long-acting oral morphine or usual care and a placebo, to measure the efficacy of additional long acting morphine in relieving postoperative pain. Following assessments over a 4 day period results indicated that the difference in pain scores between groups was statistically significant. However, these differences were not considered to be clinically significant. Furthermore, patients receiving morphine experienced more adverse effects in comparison to the control group.