Fatigue fractures involving the sacrum are extremely rare, and to our
knowledge no occurrence of such a fracture in a child has been reporte
d in the English-language literature. These fractures may mimic primar
y bone tumours or infection, and it is important to make an accurate d
iagnosis so that unnecessary biopsy can be avoided. We report a fatigu
e fracture of the sacrum in an 11-year-old child following prolonged a
erobic exercise.