26 level 1 and level 2 randomized-placebo controlled trials consisting of patients who were treated with single-dose intra-articular morphine following arthroscopic knee surgery, were included in this meta-analysis, to determine the effects of morphine on pain levels after treatment. Results indicated that the administration of morphine following arthroscopic knee surgery resulted in better pain relief, less frequent analgesic requests, and fewer patients requiring supplementary analgesia. There was no significant difference in the amount of side effects experienced when comparing morphine treatment to a placebo.