|Left elbow-joint, showing anterior and ulnar collateral ligaments.|
|Gray's||subject #84 321|
The elbow is the region surrounding the elbow-joint.
The bony prominence at the very tip of the elbow is the olecranon process of the ulna.
Two main movements are possible at the elbow:
In the anatomical position (with the forearm supine), the radius and ulna lie parallel to each other. During pronation, the ulna remains fixed, and the radius rolls around it at both the wrist and the elbow joints. In the prone position, the radius and ulna appear crossed.
Most of the force through the elbow joint is transferred between the humerus and the ulna. Very little force is transmitted between the humerus and the radius. (By contrast, at the wrist joint, most of the force is transferred between the radius and the carpus, with the ulna taking very little part in the wrist joint).
The muscles in relation with the joint are:
The arteries supplying the joint are derived from the anastomosis between the profunda and the superior and inferior ulnar collateral branches of the brachial, with the anterior, posterior, and interosseous recurrent branches of the ulnar, and the recurrent branch of the radial. These vessels form a complete anastomotic network around the joint.
The elbow-joint comprises three different portions. All these articular surfaces are enveloped by a common synovial membrane, and the movements of the whole joint should be studied together.
|humeroulnar joint||trochlear notch of the ulna||trochlea of humerus||Is a simple hinge-joint, and allows of movements of flexion and extension only.|
|humeroradial joint||head of the radius||capitulum of the humerus||Is an arthrodial joint.|
|proximal radioulnar joint||head of the radius||radial notch of the ulna||In any position of flexion or extension, the radius, carrying the hand with it, can be rotated in it. This movement includes pronation and supination.|
The combination of the movements of flexion and extension of the forearm with those of pronation and supination of the hand, which is ensured by the two being performed at the same joint, is essential to the accuracy of the various minute movements of the hand.
The hand is only directly articulated to the distal surface of the radius, and the ulnar notch on the lower end of the radius travels around the lower end of the ulna. The ulna is excluded from the wrist-joint by the articular disk.
Thus, rotation of the head of the radius around an axis passing through the center of the radial head of the humerus imparts circular movement to the hand through a very considerable arc.
The trochlea of the humerus is received into the semilunar notch of the ulna, and the capitulum of the humerus articulates with the fovea on the head of the radius. The articular surfaces are connected together by a capsule, which is thickened medially and laterally, and, to a less extent, in front and behind. These thickened portions are usually described as distinct ligaments.
The synovial membrane is very extensive. It extends from the margin of the articular surface of the humerus, and lines the coronoid, radial and olecranon fossæ on that bone; it is reflected over the deep surface of the capsule and forms a pouch between the radial notch, the deep surface of the annular ligament, and the circumference of the head of the radius. Projecting between the radius and ulna into the cavity is a crescentic fold of synovial membrane, suggesting the division of the joint into two; one the humeroradial, the other the humeroulnar.
Between the capsule and the synovial membrane are three masses of fat:
The now obsolete length unit ell relates closely to the elbow. This becomes especially visible when considering the Germanic origins of both words, Elle (ell, defined as the length of an arm from shoulder to fingertips) and Ellbogen (elbow).
It is unknown when or why the second "l" was dropped from English usage of the word, but a more precise suggested spelling would be "ellbow" for the joint and "ellbone" for the ulna, the etymological originator of both unit and joint.
When the arm is extended, with the palm facing forward or up, the bones of the humerus and forearm are not perfectly aligned. The deviation from a straight line (generally on the order of 5-10°-men, 10-25°-women) occurs in the direction of the thumb, and is referred to as the carrying angle (visible in the right half of the picture, right). In females the carrying angle is greater than in males.
Carrying angle is typically larger in women than in men, due to the wider pelvic girdle exhibited in women.
The carrying angle can influence how objects are held by individuals - those with a more extreme carrying angle may be more likely to supinate the forearm when holding objects in the hand to keep the elbow closer to the body.
Elbow arthritis is usually seen in individuals with rheumatoid arthritis. When the damage to the joint is severe, elbow replacement may be considered.
This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.
The content of this section is licensed under the GNU Free Documentation License (local copy). It uses material from the Wikipedia article "Elbow" modified December 22, 2007 with previous authors listed in its history.
Human anatomical features