Ulnar notch of the radius

{{Redirect|Sigmoid cavity|Greater sigmoid cavity|Trochlear notch}}

{{Infobox anatomy

| Name = Ulnar notch of the radius

| Latin = incisura ulnaris radii

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| Image = Gray213.png

| Caption = Bones of left forearm. Anterior aspect. (Ulnar notch visible but not labeled.)

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The articular surface for the ulna is called the ulnar notch (sigmoid cavity) of the radius; it is in the distal radius, and is narrow, concave, smooth, and articulates with the head of the ulna forming the distal radioulnar joint.