The Investigation will be conducted as a single-submission, multi-center study with approval from and in compliance of the Western Institutional Review Board (WIRB).

The overall objective of this Investigation is to assess the safety and effectiveness of the Robotic Arm Interactive Orthopedic System (RIO) Total Knee Arthroplasty Application. Specifically, the study objectives are classified as follows:

• Primary Objective: Surgeon assessment of standardized TKA complications both intra-operatively and at short term follow up.
• Secondary Objective: Radiographic assessment of post-operative limb alignment.
• Supporting Objective: Patient assessment of post-operative function and satisfaction.

Inclusion Criteria:

• Male or female subjects may be recruited in to the Investigation.
• Age - The subject must be at least 21 years of age and skeletally mature as demonstrated radiographically by complete closure of the distal femoral and proximal tibial epiphyses.
• Subjects who are able to give voluntary, written informed consent to participate in this investigation and from whom consent has been obtained.
• Subjects who, in the opinion of the Investigators and Approved Study Staff, are able to understand this Investigation and cooperate with the Investigation procedures and are willing to comply with all the required post-operative follow-ups.
• Subjects who require a total knee arthroplasty for primary surgical management of osteoarthritis, post-traumatic arthritis, rheumatoid arthritis, moderate deformities or femoral condyle osteonecrosis as defined below.
• Osteoarthritis: Kellgren-Lawrence Grade 3 or higher, with clinical history of an absence of major trauma to the joint; symptoms of pain, stiffness, swelling, and/or loss of motion; and with radiographic evidence of joint space narrowing, sub-chondral sclerosis, or peripheral osteophytes.
• Post-Traumatic Arthritis: Kellgren-Lawrence Grade 3 or higher, with a clinical history of trauma to the targeted knee and subsequent pain, stiffness, swelling and loss of motion; and with radiographic evidence of joint space narrowing, sub-chondral sclerosis, or peripheral osteophytes.
• Rheumatoid Arthritis: American College of Rheumatology classification score of 6 or higher, with a clinical history that demonstrates the following: morning stiffness for at least 1 hour and present for at least 6 weeks, swelling, loss of motion, and/or serum rheumatoid factor; and radiographic findings of narrow joint space, peri-articular osteopenia, and/or per-articular erosions.
• Moderate Deformities: Moderate varus, valgus, flexion, or post-traumatic deformities of no more than 15° assessed radiographically. Moderate recurvatum of no more than 8° assessed radiographically.
• Femoral Condyle Osteonecrosis: Loss of blood supply in the femoral condyle characterized by sudden onset of pain, possibly triggered by a specific seemingly routine activity or minor injury. Pain is often increased with activity and at night time and may cause swelling of the knee and sensitivity to touch and pressure and may result in limited motion. Confirmed by a bone scan, MRI, and/or x-ray.
• Subjects whose anatomy is appropriate for the available range of implant sizes.

Exclusion Criteria:

• Patients who have had previous surgical procedures requiring implantation of hardware in their operative side knee, hip, or ankle that would result in metal artifact scatter in a CT scan.
• Patients who have a fracture malunion of the distal femur or proximal tibia within 12cm of the knee center, assessed radiographically.
• Patients who are pregnant, may become pregnant during the course of the Investigation, or are currently lactating.
• Patients with allergies or suspected sensitivity to any patient-contacting component of the investigational device or the implant to be used in the study as listed below:
• Femoral component: Cobalt Chromium alloy (CoCr)
• Tibial component: Titanium alloy (Ti6Al4V)
• Tibial inserts and patella component: Vitamin E infused ultra-high molecular weight polyethylene (UHMWPE)
• Saw blade: 440C Stainless Steel
• Patients who require bilateral total knee arthroplasty.
• Patients who are currently on medical leave from their employment due to Workmen's Compensation.
• Patients who are currently state or federal prisoners.
• Patients who are currently Wards of the state.
• Patients who are at high risk for poor healing or confounding outcomes or at excessive risk for surgery i.e.: clinically significant/being actively treated for renal, hepatic, cardiac, hematologic, or neurologic disease or poorly controlled diabetes (HbA1c > 10 mg/dL) or previous history of joint infection.
• Patients who are known drug or alcohol abusers or with psychological disorders as defined by DSM V that could affect follow-up care or treatment outcomes.
• Patients who are currently involved in another clinical study with an investigational device.
• Patients with current litigation pending related to medical treatment of any sort.

Subject enrollment to end of study.

Participants = knees