Mobile - Bearing Knee Study

Inclusion Criteria: * Skeletal maturity * Less than 70 on preoperative Knee Society Score (Rating Score) * Sufficient bone stock, as judged by radiographs, to support primary knee implant * Patients with inflammatory tissue disorders, osteoarthritis, post-traumatic arthritis, secondary arthritis, or avascular necrosis of the femoral condyles * Patient is not pregnant * Primary total knee replacement * Sufficient collateral ligaments to support device, as judged by physician during stability testing (varus/valgus and flexion/extension) * Varus deformity \<45 or valgus deformity \<45 or fixed flexion deformity \<90 * Patient is likely to be available for evaluation for the duration of the study * Able and willing to sign the informed consent and follow study procedures Exclusion Criteria: * Skeletal immaturity * Greater than or equal to 70 on preoperative Knee Society Score (Rating Scale) * Previous knee surgery that has adversely affected bone stock or prior total knee replacement * Post patellectomy * Patient is pregnant * Insufficient collateral ligaments, as judged by the physician * Neurological conditions that might hinder patient's ability to follow study procedures (i.e., any that restrict physical activities such as Parkinson's Disease, Multiple Sclerosis, previous stroke which affects lower extremity). * Varus deformity \>45 or valgus deformity \>45 or fixed flexion deformity \>90. * Mental conditions that may interfere with ability to give an informed consent or willingness to fulfill the study requirements (i.e., severe mental retardation such that the patient cannot understand the informed consent process, global dementia, prior strokes that interfere the with patient's cognitive abilities, senile dementia, and Alzheimer's Disease). * Prisoners * Conditions that place excessive demand on the implant (i.e. Charcot's joints, muscle deficiencies, refusal to modify postoperative physical activities, skeletal immaturity).