Study to Evaluate the Performance of Navigated TKA With OrthoPilot® pheno4u TKA Level 1

Inclusion Criteria: * Indication for a TKA with the OrthoPilot® Navigation System with a Aesculap total knee endo-prosthesis * Written signed informed consent of patient * Willingness and mental ability to participate at the long-term follow-up examinations Exclusion Criteria: * Pregnancy * Patients \< 18 years or \> 80 years * Patients unable to participate at the follow-up examination (physically, mentally) * Previous joint replacement at the index knee * ASA classification \> 3 ( ASA I: A healthy patient without systemic diseases. ASA II: A patient with a mild systemic disease that is well controlled (e.g., well-controlled diabetes or hypertension). ASA III: A patient with a severe systemic disease that causes functional limitations (e.g., poorly controlled diabetes, COPD). ASA IV: A patient with a life-threatening systemic disease (e.g., severe heart failure, sepsis). ASA V: A dying patient who is not expected to survive without the operation. ASA VI: A deceased patient whose organs are being removed for donation.)