Occult ankle fracture detected by an ankle effusion on plain radiography: a case report.

Subtle ankle fractures may escape detection on plain radiography. These occult fractures can cause prolonged disability and pain. We present a case of blunt ankle trauma where plain radiography failed to reveal any bony abnormalities. The recognition of an ankle effusion on plain radiographs prompted us to perform a computed tomography (CT) scan of the ankle. The CT scan demonstrated an anterior plafond fracture of the distal tibia, which required surgical fixation. Had the fracture not been identified, our patient would have been treated inappropriately for a ligament sprain. An occult fracture should be suspected if an ankle is grossly swollen after blunt trauma, and plain radiography demonstrates an effusion. In this circumstance, performance of further imaging studies, such as conventional or CT, are advised to rule out an occult ankle fracture.