Sail sign (elbow)

Last revised by Dr Daniel J Bell on 21 Apr 2021

The sail sign on an elbow radiograph, also known as the anterior fat pad sign, describes the elevation of the anterior fat pad to create a silhouette similar to a billowing spinnaker sail from a boat. It indicates the presence of an elbow joint effusion.

The anterior fat pad is usually concealed within the coronoid fossa or seen paralleling the anterior humeral line.  When there is a joint effusion, the anterior fat pad (which is intra-articular, but extrasynovial) becomes elevated.

Elevation of the anterior fat pad usually heralds the presence of an intra-articular fracture. 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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Cases and figures

  • Figure 1: sail boat (photo)
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  • Figure 2: elbow effusion (diagram)
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  • Case 1
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  • Case 2
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  •  Case 3
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  • Case 4: MRI equivalent
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  • Case 5
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  •  Case 6
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  • Case 7
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