Xu B, Wang Y, Zeng C, et al. - A total of 10 studies were involved in a systematic review and meta-analysis in order to investigate the analgesic efficiency and safety of ketamine following total knee or hip arthroplasty. One of them was ranked as low quality. In contrast with placebo, intravenous ketamine was efficacious for pain relief during 0–8-hour though not during 8–24-hour postoperative periods, and efficient for the decrease of cumulative morphine consumption during both 0–24-hour and 0–48-hour postoperative periods, without expanding risks of gastrointestinal or psychotic adverse impacts. The limited data available for intra-articular and epidural ketamine reflected a notable decrease in pain intensity during the 8–24-hour postoperative period. In conclusion, for postoperative pain relief in patients undergoing total knee or hip arthroplasty, intravenous administration of ketamine is efficient and safe. Nonetheless, the analgesic effectiveness and safety of ketamine in such patients appear to differ by various administration routes and still guarantee additional studies to investigate.