Total knee replacement surgery is a conventional approach to alleviating the pain and lack of function resulting from arthritis of the knee. While conventional knee replacement surgery is highly successful, incidences of improperly installed replacement parts are not uncommon. To improve outcomes, robotic-assisted total knee replacement surgery has recently become available, and has been shown to be extremely effective for partial knee replacement surgery. However, further research is needed to determine if this same technology can be equally effective for total knee replacement surgery. The present study will evaluate outcomes of robotic-assisted versus conventional total knee replacement surgery in patients between 40 and 85 years old with end stage arthritis of the knee. Other than surgical technique, patients will receive the same operative care and knee replacement implants. In addition to standard x-rays, subjects will be asked to complete several short-term clinical and functional tests and questionnaires to determine outcomes of their surgery.