Introduction and Aims: Although many analgesia modalities have been tried, total knee arthroplasty remains a painful procedure and parenteral narcotics still play a major role in post-operative pain control. We want to know if peri-articular large dose injection of local anaesthetics reduces narcotics administration and their side effects. Method: Thirty-six patients undergoing a total knee replacement were randomised to two treatment groups. The experimental group received peri-articular large dose infiltration of Ropivacaine (local anaesthetic) during surgery and on day one after surgery via an intra-articular catheter. The pain control was completed with a self-delivering morphine pump. The control group received the morphine pump alone. The therapists recording post-op data were blind to the treatment group. Narcotics consumption, pain control, medication side effects, complications, range of motion and patient satisfaction were monitored. Ropivacaine serum levels were measured in the early post-operative period. Results: Although satisfaction was very high in both groups, morphine consumption was significantly lower for the infiltration group: 29 mg/24h compared to 51 mg/24 (p< 0.01) and 47 mg/40h compared to 71 mg/40h (p< 0.04). The post-operative pain evaluated with visual analogue scale (0–10) was reduced significantly on the day of surgery 2.6 vs 5.0 (p< 0.04) and at exercise on day one post-op: 4.9 vs 7.0 (p< 0.01). There was no significant difference in post-operative range of motion at five days post-op. The surgical time was increased significantly by 18 minutes in the infiltration group 126 vs 108 minutes (p< 0.05). Complication rate was not significantly different for both groups (infiltration vs control): nausea symptoms 2.2h/48h vs 5.4h/48, confusion two subjects in each group, constipation three subjects in each group and one deep vein thrombosis per group. No complication was related to the addition of the infiltration of the local anaesthetics and the serum levels were in a safe range. Conclusion: This peri-operative local anaesthetics infiltration protocol offer many benefits for the patients undergoing a total knee arthroplasty. It is improving the pain control, reducing the amount of narcotics consumption and is a safe procedure