A Study to Compare the NexGen CR and CR-Flex Knee Implants

Inclusion Criteria: * Age, 21-80 years * Sex, Male and Females will be included * BMI less than or equal to 39 * Stable Health, the patient would be able to undergo surgery and participate in a follow-up program based on physical examination and medical history. * Patient is willing and able to cooperate in follow-up therapy. * Patient exhibits pre-operative radiographic evidenced of joint degeneration consistent with TKA that cannot be treated in non-operative fashion. * Patient has stable and functional posterior cruciate and collateral ligaments. * Patient has potential to perform higher than average range of motion activities. * Operative side range of motion flexion greater than or equal to 120 degrees. * Severe knee pain and disability due to degenerative joint disease. * Patient or patient's legal representative has signed the Informed Consent form. Exclusion Criteria: * Previous history of infection in the affected joint. * Previously failed knee endoprosthesis of any kind. * Charcot joint disease or other severe neurosensory deficits. * Previous patellectomy * Patient is skeletally immature. * Grossly insufficient femoral or tibial bone stock. * Patient is pregnant. * Varus or valgus deformity greater than 20 degrees. * Fixed flexion deformity greater than 15 degrees. * Previous high tibial osteotomy. * Previous femoral osteotomy. * Patient is a poor compliance risk, currently treated for ethanol or drug abuse, physical or mental handicap, etc. * Loss of musculature or absence of musculoligamentous supporting structures required for adequate soft tissue balance.