In the elderly patients who complain of pain in the buttock and leg, it is not easy to distinguish whether the pain comes from the lesion of the hip or from the spine. A 78-year-old female who was treated conservatively for persistent pain in the right buttock and leg after an operation for spinal stenosis in the local clinic visited our clinic. Septic hip arthritis with severe femoral head destruction and multiple abscesses in the buttock and iliopsoas muscle were diagnosed 2 months postoperatively, and spinal abscess in the site of the previous operation was detected by a subsequent MRI study. To avoid such a delay of the diagnosis and treatment, it is important to suspect hip joint lesion earlier for the source of persistent pain after a spine operation. Further more, diagnostic evaluation is necessary to rule out co-infection of the spine or iliopsoas muscle when a hip joint infection exists.