Distal Portion of the Humerus

The distal portion of the humerus is often referred anatomically as the distal extremity of the humerus (see Figs. 1.11

to 1.14). The distal portion is flat, widened, and ends distally in a broad, articular surface. The distal portion contains the two condyles, medial and lateral (see Fig. 1.14).

The lateral portion of the distal articular part consists of a

smooth, somewhat semi-spherical shaped capitulum of the

humerus. The capitulum is covered with articular cartilage

on its anterior surface and articulates with the fovea of the

head of the radius. Proximal to the capitulum, there is a

slight depression in the humerus, the radial fossa. The radial

fossa provides a space for the anterior border of the head of

the radius when the elbow is fully flexed. Just medial to the

capitulum is a slight shallow groove, in which the medial

margin of the head of the radius articulates. Just proximal

to the capitulum on the anterior surface of the humerus are

several small foramina for nutrient vessels.

The medial side of the articular surface of the distal

humerus is comprised of the spool-shaped trochlea (see

Fig. 1.14). The trochlea occupies the anterior, inferior,

and posterior surfaces of the condyle. The trochlea has a

deep groove between two well demarcated borders. The

lateral border is separated from the capitulum by the shallow groove. The medial border of the trochlea is thicker,

wider, and more prominent, and projects more distally

than the lateral border. The grooved portion of the articular surface of the trochlea is shaped well to fit the articular surface of the trochlear notch of the ulna. The trochlea

is wider and deeper on the dorsal surface than on the anterior surface. Proximal to the anterior portion of the

trochlea is a small depression, the coronoid fossa. The

coronoid fossa provides a space for the coronoid process of

the ulna during flexion of the elbow. Proximal to the posterior part of the trochlea is a deep, triangular depression,

the olecranon fossa. The olecranon fossa provides a space

to accept the most proximal portion of the olecranon

when the elbow is extended. The olecranon fossa and the

coronoid fossa are separated from each other by a thin,

sometimes translucent partition of bone. The partition

may be perforated to produce a supratrochlear foramen.

The fossae are lined by a synovial membrane that extends

from the elbow joint. The margins of the fossae provide

attachment for the anterior and posterior ligaments and

joint capsule of the elbow.

Above the medial and lateral condyles are the epicondyles. These projections provide the attachment for several muscles. The medial epicondyle is larger and more

prominent than the lateral epicondyle. The medial epicondyle contains the origin of the extrinsic flexor pronator

muscles of the forearm and flexor muscles of the hand and

wrist. These include the pronator teres, flexor carpi radialis,

palmaris longus, flexor digitorum superficialis, flexor digitorum profundus, and flexor carpi ulnaris. The ulnar collateral ligaments of the elbow joint also originate from the

medial epicondyle. On the posterior surface of the medial

epicondyle is a shallow groove in which the ulnar nerve traverses.

The lateral epicondyle is smaller and less prominent than

the medial epicondyle. The lateral epicondyle contains the

origin of several muscles, including the wrist and digit

extrinsic extensor muscles and the supinator. Muscle attachments to the lateral epicondyle include the supinator, extensor carpi radialis longus, extensor carpi radialis brevis,

extensor digitorum communis, extensor carpi ulnaris, extensor digiti minimi, and anconeus. The lateral epicondyle also

provides attachment for the radial collateral ligament of the

elbow joint

Associated Joints

The humerus articulates with the scapula at the glenohumeral joint, with the ulna at the ulnohumeral joint

(trochleoulnar joint),