The rate of venous thromboembolism is unacceptable without prophylaxis. Venographic studies of patients without prophylaxis show that the deep vein-thrombosis rates range from 40-84% after total knee replacement, and rates of pulmonary embolism range from 1.5-10%. Surgeons must balance the need for thromboprophylaxis with the need to avoid bleeding complications. The purpose of this study is to evaluate the status of thrombo prophylaxis after primary total knee replacement in ALMouassat university hospital, and to improve our outcome in future, to get better results and fewer complications.