The value of indium 111 leukocyte scanning in the evaluation of painful or infected total knee arthroplasties. Evaluation of painful total knee arthroplasties (TKAs) for infection can be difficult. Indium 111 (111In) leukocyte bone scanning provides a minimally invasive technique for evaluation of possible infection. Thirty-eight patients with a painful TKA who had surgical exploration after 111In leukocyte scanning were reviewed. The scan had an accuracy of 84%, a sensitivity of 83%, and a specificity of 85%. The 111In leukocyte scans must be interpreted in conjunction with the clinical evaluation of the patient because they are less accurate for study of TKAs than of total hip arthroplasties. 