In a patient with Pellegrini-Stieda disease, radiographs of the knees were unremarkable at the time the three-phase bone scintigraphy was abnormal. The results of follow-up radiographs three months later remained normal in the left knee, where local steroid injection was given, but revealed typical positive results in the right knee with no treatment. The three-phase bone scintigraphic pattern is rather typical and antedates the radiographic changes. Thus, the radionuclide technique would provide a useful procedure for the early diagnosis and treatment of Pellegrini-Stieda disease.