Inclusion Criteria:  Has previously undergone or currently has determined to undergo a primary TKA with the specified combination of components: EVOLUTION® NitrX™ CS/CR Non-Porous Femur, EVOLUTION® NitrX™ Non-Porous Keeled Tibia and EVOLUTION® CS Tibial Insert  Has previously undergone or currently has determined to undergo a primary TKA for any of the following:  non-inflammatory degenerative joint disease including osteoarthritis, traumatic arthritis, or avascular necrosis; inflammatory degenerative joint disease including rheumatoid arthritis; correction of functional deformity; Willing to voluntarily sign the informed consent form Willing and able to comply with the protocol, able to read and complete the required forms, and willing and able to adhere to the requirements of the protocol through the 10-year postoperative follow-up visit. Previously implanted subjects must be enrolled within 14 months of their primary TKA implantation.  Prospective enrollment of a previously unimplanted contralateral knee is permitted in this study provided:  the specified combination of components (EVOLUTION® NitrX™ CS/CR Non-Porous Femur, EVOLUTION® NitrX™ Non-Porous Keeled Tibia and EVOLUTION® CS Tibial Insert) are used, all other aspects of the Inclusion/Exclusion Criteria are satisfied, enrollment does not exceed the subject count specified in the Clinical Trial Agreement, and the subject agrees to a second Informed Consent document and data collection specific to the second TKA.  Bilateral subjects can have both TKAs enrolled in the study provided:  the specified combination of components (EVOLUTION® NitrX™ CS/CR Non-Porous Femur, EVOLUTION® NitrX™ Non-Porous Keeled Tibia and EVOLUTION® CS Tibial Insert) were implanted in both, all other aspects of the Inclusion/Exclusion Criteria are satisfied, enrollment does not exceed the subject count specified in the Clinical Trial Agreement, and the subject agrees to a second Informed Consent document and data collection specific to the second TKA.  Bilateral implantation can occur at different time periods for the same subject.  Exclusion Criteria:  Skeletally immature (less than 21 years of age) at time of implantation Has or had an overt infection at the time of implantation Has or had a distant foci of infections (which may cause hematogenous spread to the implant site) at the time of implantation Has or had a rapid disease progression as manifested by joint destruction or bone absorption apparent on roentgenogram at the time of implantation Has or had inadequate neuromuscular status (e.g., prior paralysis, fusion, and/or inadequate abductor strength), poor bone stock, poor skin coverage around the joint which would make the procedure unjustifiable Currently enrolled in another clinical investigation which could affect the endpoints of this protocol Has documented substance abuse issues Has an emotional or neurological condition that would pre-empt their ability or willingness to participate in the study Currently incarcerated or has impending incarceration Has a medical condition, as judged by the Investigator, that would interfere with the subject's ability to comply with the requirements of the protocol