The cause of pain in a patient with an apparently solidly fixed total hip arthroplasty can be difficult to elucidate. A detailed history, careful examination, and plain radiographs provide the most useful information, especially in excluding causes not primarily related to the hip. Determining whether the pain is related to the implant, to soft tissue, or to bone can require laboratory tests, radiographic and fluoroscopic imaging, and contrast arthrography and local anesthetic injections. Particularly when pain is caused by occult infection, erythrocyte sedimentation rate, C-reactive protein level, hip aspiration, advanced radiologic imaging, and nuclear medicine scans can help determine the diagnosis.