olecranon

The olecranon is a large, thick, curved bony eminence of the forearm that projects behind the elbow. It is situated at the upper (proximal) end of the ulna, one of the two bones in the forearm. When the hand faces forward the olecranon faces towards the back (posteriorly). It is bent forward at the summit so as to present a prominent lip which is received into the olecranon fossa of the humerus in extension of the forearm. Its base is contracted where it joins the body and the narrowest part of the upper end of the ulna. Its posterior surface, directed backward, is triangular, smooth, subcutaneous, and covered by a bursa. Its superior surface is of quadrilateral form, marked behind by a rough impression for the insertion of the Triceps brachii; and in front, near the margin, by a slight transverse groove for the attachment of part of the posterior ligament of the elbow-joint. Its anterior surface is smooth, concave, and forms the upper part of the semilunar notch. Its borders present continuations of the groove on the margin of the superior surface; they serve for the attachment of ligaments, viz. , the back part of the ulnar collateral ligament medially, and the posterior ligament laterally. From the medial border a part of the Flexor carpi ulnaris arises; while to the lateral border the anconeus muscle is attached. Every claim on this page comes from the Leumas anatomy graph and carries its source.

What the olecranon is

The olecranon is a large, thick, curved bony eminence of the forearm that projects behind the elbow. It is situated at the upper (proximal) end of the ulna, one of the two bones in the forearm. When the hand faces forward the olecranon faces towards the back (posteriorly). It is bent forward at the summit so as to present a prominent lip which is received into the olecranon fossa of the humerus in extension of the forearm. Its base is contracted where it joins the body and the narrowest part of the upper end of the ulna. Its posterior surface, directed backward, is triangular, smooth, subcutaneous, and covered by a bursa. Its superior surface is of quadrilateral form, marked behind by a rough impression for the insertion of the Triceps brachii; and in front, near the margin, by a slight transverse groove for the attachment of part of the posterior ligament of the elbow-joint. Its anterior surface is smooth, concave, and forms the upper part of the semilunar notch. Its borders present continuations of the groove on the margin of the superior surface; they serve for the attachment of ligaments, viz. , the back part of the ulnar collateral ligament medially, and the posterior ligament laterally. From the medial border a part of the Flexor carpi ulnaris arises; while to the lateral border the anconeus muscle is attached. The atlas records it as a bone at the organ scale in the human body.

Where the olecranon is

It sits in the upper limb, within the skeletal system. Not positioned individually. Drawn inside the structure this dataset says contains it — the containment is asserted, the exact spot within it is not.

What the olecranon connects to

The atlas records 4 typed relationships for it, across 3 kinds of connection. part of proximal epiphysis of ulna.

Supply and innervation

This dataset asserts no arterial supply, venous drainage or innervation for the olecranon. Only a minority of structures carry those edges here, so an empty answer means nothing has been recorded — not that there is nothing to record.

Also called

Also recorded as olecranon process of ulna, olecranon process and ulnar process. Searching any of those names reaches this page.

Source

Uberon multi-species anatomy ontology (Mungall et al.), CC BY 4.0. Term UBERON:0006810, version 2026-06-19, retrieved 2026-08-24. Licence: CC-BY-4.0.

Part of: proximal epiphysis of ulna.
A kind of: zone of long bone.
inserts into: anconeus muscle and triceps brachii.

Questions

Where is the olecranon?

What does the olecranon connect to?

Part of: proximal epiphysis of ulna.

Is the olecranon the same in other species?

Leumas holds the same relationship vocabulary for every species it carries, so where another dataset records this structure you can put the two side by side on /compare.