Total knee arthroplasty has excellent clinical and functional results in patient with severe gonarthrosis; however, 20% of the patients continue to experience pain following total knee arthroplasty. Systematic and careful evaluation is needed to find the main cause of pain in these patients. The evaluation of the painful knee includes an extended history, analysis the type of the pain, psychological exploration, thorough clinical examination, laboratory tests, joint aspiration if needed, test infiltrations, radiographic analysis and special imaging techniques. Using these diagnostic modalities we try to find the reason of the pain and appropriate treatment for the patient. Revision surgery should not be performed before the causative pain mechanism is well understood.