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The olecranon is situated at the proximal end of the ulna, one of the two bones in the forearm. [1] 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 during extension of the forearm. [2] [3]
In comparative anatomy, the more neutral term entepicondyle is used. The medial epicondyle gives attachment to the ulnar collateral ligament of elbow joint , to the pronator teres , and to a common tendon of origin (the common flexor tendon ) of some of the flexor muscles of the forearm : the flexor carpi radialis , the flexor carpi ulnaris ...
Between these two bands a few intermediate fibers descend from the medial epicondyle to blend with a transverse band which bridges across the notch between the olecranon and the coronoid process. This ligament is in relation with the triceps brachii and flexor carpi ulnaris and the ulnar nerve , and gives origin to part of the flexor digitorum ...
Close to the elbow, the ulna has a bony process, the olecranon process, a hook-like structure that fits into the olecranon fossa of the humerus. This prevents hyperextension and forms a hinge joint with the trochlea of the humerus. There is also a radial notch for the head of the radius, and the ulnar tuberosity to which muscles attach.
The flexor carpi ulnaris has two heads; a humeral head and ulnar head. The humeral head originates from the medial epicondyle of the humerus via the common flexor tendon. The ulnar head originates from the medial margin of the olecranon of the ulna and the upper two-thirds of the dorsal border of the ulna by an aponeurosis.
It contains tendons of the flexor digitorum superficialis and the flexor digitorum profundus, but not the flexor pollicis longus. [ 2 ] The sheath which surrounds the flexor digitorum extends downward about halfway along the metacarpal bones , where it ends in blind diverticula around the tendons to the index , middle , and ring fingers .
The styloid process of the ulna projects from the medial and back part of the ulna. It descends a little lower than the head. The head is separated from the styloid process by a depression for the attachment of the apex of the triangular articular disk, and behind, by a shallow groove for the tendon of the extensor carpi ulnaris muscle.
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 .