Left elbow, showing medial and lateral views.
The elbow joint is a ginglymus or hinge joint. Three bones form the elbow joint: the humerus of the upper arm, and the radius and ulna — the main pair of bones of the forearm. The bony prominence at the very tip of the elbow is the olecranon process of the ulna. The radius is positioned laterally to the ulna at the elbow joint.
Two main actions or movements are possible at the elbow:
The complex action of turning the forearm over (pronation or supination) happens at the articulation between the radius and the ulna (this movement also occurs simultaneously at the wrist joint).
The combined motion of these joints allows a range of motion from 5-150° of flexion-extension and 75° of pronation to 80° of supination. Remember that the olecranon process of the ulna sits in the humeral olecranon fossa in 20° or less of flexion.
In the anatomical position (with the forearm supine or in supination), 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.
During exertion, 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. Interestingly — and in contrast — at the wrist joint, most of the force is transferred between the radius and the carpus, with the ulna attenuating little force in the wrist joint.
Muscles, arteries, and nerves
The muscles in relation with the joint are:
Triceps brachii and Anconeus
Supinator, and the common tendon of origin of the forearm Extensor muscles
The common tendon of origin of the forearm Flexor muscles, and the Flexor carpi ulnaris.
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 nerves of the joint are a twig from the ulnar, as it passes between the medial condyle and the olecranon; a filament from the musculocutaneous, and two from the median.
Ligaments of the elbow
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 major ligaments are the ulnar collateral ligament, radial collateral ligament, and annular ligament. The ligaments are actually thick extensions of the capsule, rather than true ligaments. Of the 3 medial structures, the anterior medial collateral ligament (AMCL) is the most important, providing approximately 70% of the valgus stability. On the lateral elbow, the lateral ulnar collateral ligament (LUCL) is the strongest of the 4 branches, providing varus support.
X-ray showing a flexed elbow (left), and an extended right elbow (right) that shows the angle of the humerus compared to the radius and ulna.
When the arm is extended, with the palm facing forward or up (supination), the upper arm is not in straight alignment with the forearm. The deviation from a straight line (generally on the order of 5-10°) occurs in the direction of the thumb (in supination), and is referred to as the carrying angle (visible in the right half of the picture of x-ray above). In females the carrying angle is usually greater than the carrying angle in males.
The carrying angle can influence how objects are held by individuals and may decrease efficiency of elbow flexion and elbow flexion force production. Increased carrying angle causes increased valgus stress on the medial structures of the elbow.
Some individuals are also born with elbows that have a larger range of motion with hyperextension. The elbow may be subject to instability and pain and by slightly dysfunctional if it is capable of hyperextended range of motion.
Elbow Injury Risk
Elbows are at risk of overuse injuries and accidental trauma. Structures in the elbow that are subject to injury are bones, ligaments and muscle tendons. Nearby muscles can also be a source of problems. The following conditions are associated with elbow medical issues: biceps tendinosis, biceps tendinopathy, biceps tendonitis, anterior capsule strain, pronator syndrome, median nerve compression syndrome, lateral epicondylitis (tennis elbow), medial epicondylitis (tennis elbow), radial tunnel syndrome, posterior interosseous nerve compression syndrome, triceps tendinosis, triceps tendinopathy, triceps tendinitis, olecranon impingement syndrome, posterior impingement syndrome, hyperextension valgus overload syndrome, boxer’s elbow, olecranon stress fractures, radiocapitellar chondromalacia, and posterolateral rotatory instability.
Activity that causes increased valgus stress on the elbow can cause ulnar nerve injury, posterior impingement syndrome, or olecranon stress fractures.
The elbow and forearms in sports are often involved in contact with other players, the floor or ground during falls or catches. Elbows can also be hit by pitches in baseball or hockey pucks in hockey.
Pitchers with excessive innings are more likely to
Idioms of the elbow
at my elbow
within convenient reach
Performing hard work, especially when you are cleaning or rubbing something
1. space to move around. 2. unrestrained thinking for better creativity and politics — the freedom to think what one wants.
give the elbow
to break off a romantic relationship
more power to your elbow
to wish someone good luck
to hang out or get the opportunity to talk with someone who is famous or accomplished in their field