EVOLUTION® Revision STEMMED CS Post Market Clinical Follow-up Study Protocol

Inclusion Criteria: 1. Has previously undergone or currently has been determined to undergo a revision knee arthroplasty that requires implantation of the components under study (EVOLUTION® Revision Tibial System and EVOLUTION® STEMMED CS Femur with the EVOLUTION® MP CS Tibial Insert) 2. Decision to perform the study index surgery with the required study components is pre-determined regardless of the research; 3. Previously implanted subjects must be enrolled within 3 years (+ 6 months) of their study index surgery 4. Willing to voluntarily sign the informed consent form 5. 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. Exclusion Criteria: 1. Skeletally immature (less than 21 years of age) at time of implantation 2. Has or had an overt infection at the time of implantation 3. 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 4. Currently enrolled in another clinical investigation which could affect the endpoints of this protocol 5. Has or had documented substance abuse issues 6. Has or had an emotional or neurological condition that would pre-empt their ability or willingness to participate in the study 7. Currently incarcerated or has impending incarceration 8. 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