Trochlear notch

The trochlear notch (also semilunar notch, or greater sigmoid cavity) is a large depression in the upper extremity of the ulna that fits the trochlea of the humerus (the bone directly above the ulna in the arm) as part of the elbow joint. It is formed by the olecranon and the coronoid process.

Trochlear notch
Upper extremity of left ulna. Lateral aspect. (Semilunar notch visible at center top.)
LatinIncisura trochlearis ulnae,
incisura semilunaris ulnae
Anatomical terms of bone

About the middle of either side of this notch is an indentation, which contracts it somewhat, and indicates the junction of the olecranon and the coronoid process.

The notch is concave from above downward, and divided into a medial and a lateral portion by a smooth ridge running from the summit of the olecranon to the tip of the coronoid process.

The medial portion is the larger, and is slightly concave transversely; the lateral is convex above, slightly concave below.


This article incorporates text in the public domain from page 215 of the 20th edition of Gray's Anatomy (1918)

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