Primary Research Questions:

1. Do patients with knee osteoarthritis (OA) who undergo total knee replacement with a Sigma rotating platform have better clinical outcomes at 2 years post surgery (i.e. quality of life, function, range of motion) than similar patients who undergo total knee arthroplasty (TKA) using the Sigma fixed bearing knee?
2. Do patients with knee OA who undergo TKA with a Sigma rotating platform have different knee kinetics and kinematics as measured by gait analysis than similar patients who undergo TKA using the Sigma fixed bearing knee?
3. Do patients with knee OA who undergo TKA with or without computer assistance have better clinical outcomes at two years following surgery (quality of life, function, range of motion)?
4. Do patients with knee OA who undergo TKA with or without computer assistance have different knee kinematics and kinetics as measured by gait analysis?

Inclusion Criteria:

• Age 45-75 years
• Undergoing primary total knee arthroplasty
• Clinically significant osteoarthritic degeneration

Exclusion Criteria:

• Active articular infections
• Bilateral knee replacement (simultaneous)
• Previous joint infections
• Significant concurrent ipsilateral hip osteoarthritis
• Chronic pain syndrome requiring medications for control
• History of chemical addiction
• Significant spinal stenosis, significant symptomatic sciatica
• Patients who are unlikely to comply with, participate in, or return for follow-up visits as described in the protocol
• Osteomyelitis, septicemia or other infections that may spread to other areas of the body
• Highly communicable diseases, immuno-compromising conditions and/or conditions that may limit follow-up (eg. AIDS, active tuberculosis, venereal disease, active hepatitis, neoplastic disease)
• Decreased mental comprehension and literacy
• Prior high tibial osteotomy
• Prior patellectomy
• Rheumatoid arthritis
• Pregnancy