Stress fracture of femoral neck
This 29 year old female jogger presented with progressively worsening right hip pain. Her radiograph is normal, left, however the sensitivity of plain films for early stress fractures is low so an MRI was requested (a bone scan would be a reasonable alternative test). The coronal STIR sequence (a form of fat-suppressed imaging that is very sensitive to marrow oedema) on the right shows a subtle low signal fracture line (yellow arrow) surrounded by extensive high signal marrow oedema (white arrows). This is an important diagnosis to make, as stress fractures like this can become complete and displaced (requiring surgery) if the patient continues running.