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Case of the Month 06/08

This patient presented complaining of knee pain after a fall. Q: What is the abnormal finding in the xray below and what is it's significance?

View answer

There is a fat-fluid level (called a lipohemarthrosis). This is due to escape of fatty marrow from the bone after a fracture.

Q: How is the x-ray demonstrating this finding different from the normal knee series?

View answer

A normal knee series is made up of an AP and lateral view. These are done with the patient laying supine and lateral (respectively). The best view to visualize the lipohemarthrosis is the cross-table lateral as seen above. It is also easily visualized on CT (see below).