Bone: Olecranon
Upper extremity of left ulna. Lateral aspect.
Gray's	subject #52 214

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 (supination) 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.

[edit] See also

• Elbow-joint

It is also the insertion of all three heads of the triceps brachii.

[edit] Additional images

Bones of left forearm. Anterior aspect.	Plan of ossification of the ulna. From three centers.	Left elbow-joint, showing anterior and ulnar collateral ligaments.	Capsule of elbow-joint (distended). Posterior aspect.
Posterior surface of the forearm. Deep muscles.	The Supinator.

[edit] External links

• Olecranon at eMedicine Dictionary
• radiographsul at The Anatomy Lesson by Wesley Norman (Georgetown University) (xrayelbow)
• Roche Lexicon - illustrated navigator, at Elsevier 02240.008-1

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.

v • d • e Bones of upper limbs (TA A02.4, GA 2.200-230) Pectoral girdle, clavicle conoid tubercle · trapezoid line · costal tuberosity · subclavian groove Scapula fossae (subscapular, supraspinatous, infraspinatous) · suprascapular notch · glenoid cavity tubercles (infraglenoid, supraglenoid) · spine of scapula · acromion · coracoid process borders (superior, lateral/axillary, medial/vertebral) · angles (superior, inferior, lateral) Humerus upper extremity: necks (anatomical, surgical) · tubercles (greater, lesser) · intertubercular sulcus body: radial sulcus · deltoid tuberosity lower extremity: capitulum · trochlea · epicondyles (lateral, medial) · supracondylar ridges (lateral, medial) · fossae (radial, coronoid, olecranon) Forearm radius: upper extremity (head, tuberosity) · body · lower extremity (ulnar notch, styloid process) ulna: upper extremity (tuberosity, olecranon, coronoid process, radial notch, trochlear notch) · body · lower extremity (head, styloid process) Hand carpus: scaphoid · lunate · triquetral · pisiform · trapezium · trapezoid · capitate · hamate (hamulus) metacarpus: 1st metacarpal · 2nd · 3rd · 4th · 5th phalanges of the hand: proximal · intermediate · distal

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