Elbow joint effusion - sail sign

Case contributed by Frank Gaillard

Presentation

Trauma

Note: This case has been tagged as "legacy" as it no longer meets image preparation and/or other case publication guidelines.

x_ray

On lateral elbow radiograph, the anterior fat pad (which is intra-articular, but extra-synovial) becomes elevated due to joint effusion appearing as a triangle. This has been termed the sail sign due to the resemblance to the spinnaker of a sailboat. 

There is also on sagittal CT, the fat pads of the elbow become elevated due to joint effusion.

Case Discussion

There is elevated anterior fat pad of the elbow due to joint effusion which is called sail sign.

In adults, this is usually a radial head fracture whereas in children, the commonest cause of a raised elbow fat pad is a supracondylar fracture.  Where a fat pad is raised and no fracture is demonstrated, an occult fracture should be suspected.

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