"The Unhappy Total Knee Replacement" is a specialized book that focuses on improving diagnostic and treatment guidelines for patients who have experienced unsatisfactory outcomes following total knee arthroplasty (TKA). The book begins with an introduction to the fundamentals of TKA and highlights the various causes of failures and pain. It offers a detailed examination of diagnostic aspects, including advanced clinical examinations, laboratory analyses, and particularly imaging techniques. Additionally, modern diagnostic algorithms are presented to assist readers in better navigating the challenges in clinical practice. The book discusses specific treatment-related options, including conservative approaches as well as strategies for salvage and revision surgeries, emphasizing important pitfalls and key points. A series of illustrative cases demonstrate common clinical scenarios encountered in daily practice. The evidence-based, clinically focused guidance, authored by internationally recognized experts, aids surgeons in achieving the most effective treatment for these challenging cases.