The olecranon (, ), is a large, thick, curved bony

process A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic. Things called a process include: Business and management * Business process, activities that produce a specific s ...

on the proximal, posterior end of the

ulna The ulna or ulnar bone (: ulnae or ulnas) is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the Radius (bone), radius, the forearm's other long ...

. It forms the protruding part of the

elbow The elbow is the region between the upper arm and the forearm that surrounds the elbow joint. The elbow includes prominent landmarks such as the olecranon, the cubital fossa (also called the chelidon, or the elbow pit), and the lateral and t ...

and is opposite to the

cubital fossa The cubital fossa, antecubital fossa, chelidon, inside of elbow, or, humorously, wagina, is the area on the anterior side of the upper part between the arm and forearm of a human or other hominid animals. It lies anteriorly to the elbow (antecubit ...

or elbow pit (

trochlear notch The trochlear notch (), also known as semilunar notch and greater sigmoid cavity, is a large depression in the upper extremity of the ulna The ulna or ulnar bone (: ulnae or ulnas) is a long bone in the forearm stretching from the elbow to ...

). The olecranon serves as a lever for the

extensor muscles In anatomy, extension is a movement of a joint that increases the angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extendi ...

that straighten the elbow joint.

Structure

The olecranon is situated at the proximal end of the ulna, one of the two bones in the

forearm The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is used to describe the entire appendage of the upper limb, but which in anatomy, techn ...

. When the hand faces forward (

supination Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relativ ...

) 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 The olecranon fossa is a deep triangular depression on the posterior side of the humerus, superior to the trochlea. It provides space for the olecranon of the ulna during extension of the forearm. Structure The olecranon fossa is located ...

of the

humerus The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

during 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 Bursa () is a city in northwestern Turkey and the administrative center of Bursa Province. The fourth-most populous city in Turkey and second-most populous in the Marmara Region, Bursa is one of the industrial centers of the country. Most of ...

. Its superior surface is of quadrilateral form, marked behind by a rough impression for the insertion of the

triceps brachii The triceps, or triceps brachii (Latin for "three-headed muscle of the arm"), is a large muscle on the back of the upper limb of many vertebrates. It consists of three parts: the medial, lateral, and long head. All three heads cross the elbow jo ...

; 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 The trochlear notch (), also known as semilunar notch and 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 ...

. 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 The flexor carpi ulnaris (FCU) is a skeletal muscle, muscle of the forearm that flexion, flexes and Adduction, adducts at the wrist joint. Structure Origin The flexor carpi ulnaris has two heads; a humeral head and ulnar head. The humeral head o ...

arises; while to the lateral border the

anconeus muscle The anconeus muscle (or anconaeus/anconæus) is a small muscle on the posterior aspect of the elbow joint. Some consider anconeus to be a continuation of the triceps brachii muscle. Some sources consider it to be part of the posterior compartmen ...

is attached.

Clinical significance

Fractures of the olecranon are common injuries. An olecranon fracture with anterior displacement of the radial head is called a

Hume fracture The Hume fracture is an injury of the elbow comprising a fracture of the olecranon with an associated anterior dislocation of the radial head which occurs in children. It was originally described as an undisplaced olecranon fracture, but more rece ...

Etymology

The word "olecranon" comes from the ''

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

'' ''olene,'' meaning elbow, and ''kranon,'' meaning head.

Additional images

File:En-elbow joint.svg,

Upper extremity The upper Limb (anatomy), limbs or upper extremities are the forelimbs of an upright posture, upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digit (anatomy), digits, including all the musc ...

of left

. Lateral aspect File:Gray213.png, Bones of left forearm. Anterior aspect. File:Gray215.png, Plan of ossification of the ulna. From three centers. File:Gray329.png, Left elbow-joint, showing anterior and ulnar collateral ligaments. File:Gray332.png, Capsule of elbow-joint (distended). Posterior aspect.

References

External links