This study will be conducted at a single centre. The study has two treatment groups. One group of 50 knees (approximately 50 subjects) will have a surgical method that uses mechanical alignment (alignment based on how the leg and knee joint move) to determine the proper position of the knee replacement device. The other group of 50 knees (approximately 50 subjects) will have a surgical method that uses anatomical alignment (alignment based on how the anatomy/structure of the leg and knee joint) determine the proper position of the knee replacement device. Subjects will be randomly assigned to one of the two groups. Clinical and functional tests will be conducted pre-operatively and at 6 weeks, 3 months, 6 months and 12 months to determine overall knee function. In addition, a CT scan will be completed pre-operatively and at 6 weeks to assess changes in alignment.