We report the findings of a randomised controlled triple-blind pilot study of intraoperative ketamine infusion combined with spinal anaesthesia on the prevalence of persisting post surgical pain following total knee arthroplasty surgery. Twelve patients were randomised to receive either ketamine or placebo in association with spinal anaesthesia for total knee arthroplasty. All patients also received general anaesthesia. More patients were pain-free at six months in the ketamine group (three of five) compared to the control group (two of seven). Perioperative data collected during the study suggested that the addition of intraoperative ketamine might also improve the quality of recovery. Although no statistical analysis was undertaken due to the small numbers, these preliminary findings suggest that the use of intraoperative systemic ketamine in association with spinal anaesthesia for the reduction of persisting post surgical pain deserves further study.