Thirty subjects who are scheduled to receive an Empowr PS Total Knee Replacement device will be consented to be in the prospective component of the study. Twenty of these patients will participate in motion data collection. These patients will all be scheduled to undergo primary total knee replacement using the Empowr device. All surgeries will be performed using computer navigation. Patients will receive standardized physical therapy to insure consistency of rehab protocols and discharge from physical therapy criteria. Specifically, patients will be monitored for visit compliance, Timed Up and Go (TUG) test in seconds, AROM in degrees, and walking un-aided.

Data were previously collected preoperatively, at 6 months and 1 year post-operatively for 16 patients who received a Stryker Triathlon total knee replacement and preoperatively and 1 year post-op for 16 patients who received a Biomet Vanguard total knee replacement. Data were also previously collected for 20 age matched healthy controls subjects. Data will be collected for an additional 20 control subjects. Knee Society Score (KSS) and Knee Injury and Osteoarthritis Outcome Score (KOOS) will be collected at pre-op, 6 months, 1 year, and 2 years post-op. Gait analysis data will include kinetic, kinematic, temporal spatial, and electromyographic (EMG) data throughout the gait cycle for both research subjects and controls. Reflective markers will be placed on subject's anatomical landmarks, and ten surface EMG electrodes placed according to published standards (8). Subjects will walk at a self-selected speed down a runway embedded with force plates while 10 Eagle-4 digital infrared cameras record their movement. In addition to the level surface walking, additional data on more complex activities of daily living will be collected for potential future analysis. This would include: sit-to-stand, balance, and stair-climbing measurements also using the force plates, camera system and EMG data collection.