In patients undergoing total knee arthroplasty, thromboembolism is a common occurrence, especially following tourniquet deflation. The resulting cardiopulmonary emboli can potentially lead to hypoxemia, hypotension, hemodynamic collapse and post operative cognitive dysfunction due to emboli. The standard surgical technique involves placing an intramedullary rod in the femur to determine the angle and degree of resection from the end of the femur. A new surgical technique utilizes computer navigation system to perform the desired cuts in the appropriate position. The investigators hypothesize that the avoidance of intramedullary instrumentation in computer assisted total knee replacement will result in fewer thromboembolic events compared with the standard technique using manual instrumentation in the femur. The present study will test this hypothesis by quantifying the extent of thromboembolism during both surgical techniques.