Although total knee arthroplasty predictably provides relief of pain and good functional results, a number of potential etiologies exist for a painful total knee replacement. It is paramount to exclude infection whenever evaluating a painful total knee. Results of treatment will not be satisfactory if the mechanism of pain or knee failure is not understood. There is no role for exploratory revision surgery. A complete history, physical examination, and thoughtful differential diagnosis help make the diagnosis and develop an effective treatment paradigm.200