Aim. To evaluate safety and efficacy of performing a total knee arthroplasty (TKA) on patients receiving continuous Warfarin therapy. Methods. We identified 24 consecutive patients receiving long term warfarin therapy who underwent total knee arthroplasty between 2006 and 2008. As a control, we collected the same data from a group of age and sex matched patients not on warfarin. Primary observations were changes in haemoglobin, transfusion rates and complications. Secondary observations were fluctuations in the INR and post operative range of motion (ROM). All procedures were performed by the senior author in a single centre using the same TKA technique. Results. There was no significant difference between the warfarinised and non warfarinised groups in preoperative or postoperative haemoglobin. After unilateral TKA 38% of non warfarinised patients and 24% of warfarinised patients required a blood transfusion. Both the warfarin and non warfarin groups had a bilateral TKA transfusion rate of 67%. In the warfarin group the mean preoperative INR was 2.2 (SD=0.46; range 1.0 to 3.0) and mean postoperative INR was 2.6 (SD=0.8; range 1.5 to 5.0). There were no surgical delays due to a high INR level. The mean change in INR during the perioperative phase was minimal (mean 0.4; SD=0.7). In the warfarin group the mean flexion range of motion was 116° preoperatively, 88° at 5 days, 107° at 6 weeks and 117° at 12 months after surgery. There was no significant ROM difference between the warfarin and non warfarin groups. There were no post operative bleeding complications. Conclusions. Current American College of Chest Physicians (ACCP) guidelines recommend
