Antero-Posterior Knee Stability

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.