Intra-articular morphine compared with both bupivacaine and placebo: 6 RCTs (345 participants).
Intra-articular morphine compared with placebo: 3 RCTs (100 participants).
Cross route comparisons: 3 RCTs (144 participants).
Morphine dose response: 4 RCTs (one included above) (261 participants).
Intra-articular morphine compared with both bupivacaine and placebo: Of the 4 trials with internal sensitivity, 3 found significantly lower early pain visual analogue scale pain intensity (VASPI) scores compared with placebo. In the late period, all 3 evaluable sensitive studies reported that morphine produced significantly lower (VASPI). In the two sensitive studies where this was analysed, the morphine group had fewer additional analgesics. In two trials, which failed to demonstrate internal sensitivity, no difference was found between intra-articular morphine and placebo in either the early or late period, or in analgesic consumption.
Intra-articular morphine compared with placebo: In both the early and late period, morphine VASPI scores were significantly lower in 2 of the 3 studies. Additional analgesic consumption was also lower in 2 out of 3 studies.
Cross route comparisons: Only one trial showed greater early efficacy of intra-articular morphine compared with intravenous morphine. No significant differences were found in the late measures.
Morphine dose response: no dose response was detected.