Sacral stress fracture in a young-adult, long-distance runner: an underestimated cause of low back pain.

Sacral stress fractures (SSFs) in physically active young patients are frequently misdiagnosed due to the lack of specificity of signs and symptoms. Over the last years, these injuries have been described as rare, although some studies report that the incidence of an SSF in athletes may be as high as 20%.We describe a case of a male long-distance runner in his late 20s with a 1-month undiagnosed SSF. The patient complaints included insidious right low back and buttock pain without trauma that started after running a marathon. MRI revealed an extensive area of bone marrow oedema in the right sacral ala consistent with an SSF.This case highlights the importance of investigating SSF in young-athlete patients who were otherwise healthy, using appropriate imaging modalities to assess the presence and morphology of a fracture.