A retrospective one-time evaluation of total knee patients one year or more postoperative, to compare antero-posterior (AP) stability with the TELOS Stress device/stress x-rays and clinical outcomes. Multiple implant brand/models will be included in the study.

Inclusion Criteria:

• Patients willing to sign the informed consent.
• Patients able to comply with study requirements including stress x-rays and self-evaluations.
• Male and non-pregnant females ages 21 - 80 years of age at the time of surgery.
• Patients who have undergone a primary total knee replacement, are one year or greater postoperative, and are not having any evidence of failure of their implants.
• Patients with a diagnosis of osteoarthritis (OA), traumatic arthritis (TA), or avascular necrosis (AVN).
• Patients with intact collateral ligaments.
• Range of motion within five degrees of full extension and a minimum of 120 degrees of flexion.

Exclusion Criteria:

• Patients with inflammatory arthritis.
• Patients that are morbidly obese, body mass index (BMI) > 40.
• Patients that have had a high tibial osteotomy or femoral osteotomy.
• Patients with neuromuscular or neurosensory deficiency, which would limit the ability to assess the performance of the device.
• Patients with a systemic or metabolic disorder leading to progressive bone deterioration.
• Patients that are immunologically compromised, or receiving chronic steroids (>30 days), excluding inhalers.
• Patients bone stock is compromised by disease or infection, which cannot provide adequate support and/or fixation to the prosthesis.
• Patients with knee fusion to the affected joint.
• Patients with an active or suspected latent infection in or about the knee joint.
• Patients that are prisoners.

Internal database of prior total knee replacement patients.