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.

Currently, Transesophageal Echocardiography (TEE) is routinely used intraoperatively to monitor patients undergoing total knee arthroplasty for thromboembolic events. Video recording (without any patient identifiers) of the TEE loops before and after tourniquet release, offline analysis to quantify the extent of thromboembolism and the two surgical techniques will be compared. Patients are assigned to a particular technique according to some non-rigid criteria. This study has no impact on their selection into one group or the other. Participation in this study does not influence the choice/selection. We will simply record and analyze the echo loops in twenty patients already assigned to each surgical technique.

Inclusion Criteria:

• Adult patients scheduled to undergo Total Knee Arthroplasty at UC Davis Medical Center
• 18 years and above

Exclusion Criteria:

• Any contraindication to perform TEE

Patients scheduled for elective total knee replacement