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Anatomy of the elbow joint
Last reviewed: 04.07.2025
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The elbow joint is formed by the articular surface of the lower epiphysis of the humerus, its block and head, and the articular surfaces of the ulna and radius. There are three joints in the elbow joint cavity: humeroulontal, humeroradial, and radioulnar. The joint capsule covers the elbow joint on all sides. The elbow joint is stabilized by lateral ligaments: the ulnar and radial collateral ligaments. There is also a radial circular ligament that strengthens the radioulnar joint and ensures stability of the relationship between the radius and ulna during pronation and supination of the forearm. The anterior and posterior sections of the elbow joint are insufficiently strengthened by ligaments. The bony landmarks for examining the elbow joint are the medial and lateral epicondyles of the humerus and the olecranon process of the ulna. On the anteromedial surface, the bony landmarks are the tuberosity of the radius and the coronoid process of the ulna.
Three muscles are responsible for flexion of the forearm: the brachialis, brachioradialis, and biceps brachii. The tendons of the corresponding muscle groups are attached to the epicondyles. The tendons of the flexor muscles are attached to the medial epicondyle: the tendon of the pronator teres, the fibers of which lie the deepest; the superficial fibers of the common tendon of the flexors of the fingers; the tendon of the radial flexor carpi, superficial flexor digitorum, and flexor carpi ulnaris. The tendons of the extensor muscles are attached to the lateral epicondyle of the humerus along the posterolateral surface: the common tendon of the extensors of the fingers, the extensor carpi ulnaris, the long extensor digitorum, the short extensor digitorum, and the radial extensor carpi.
The triceps tendon, formed from the long, outer and inner heads of the muscles, is attached to the olecranon.
Between the epicondyles on the back surface above the olecranon is the olecranon fossa. There are several bursae in the elbow joint. The olecranon bursa is located at the attachment site of the triceps tendon and consists of three sections: subcutaneous, intertendinous and subtendinous. The biceps tendon bursa is located behind the tendon, at the site of its attachment to the tuberosity of the radius. The supracondylar bursae (medial and lateral) lie under the tendons above the corresponding epicondyles.
The ulnar nerve is formed from the C8-T1 nerve roots with possible involvement of C7. It innervates the medial half of the flexor digitorum profundus, flexor carpi ulnaris, hypothenar muscles, interosseous muscles, deep head of flexor digitorum brevis, and lumbrical muscles of the 3rd and 4th phalanges. It also supplies sensation to the 5th and half of the 4th digit. At the shoulder, it travels in a neuromuscular bundle with the brachial artery and medial nerve.
In the middle of the arm it follows the direction of the posterior surface of the medial epicondyle. Here it lies in the intercondylar groove between the medial epicondyle and the olecranon. Leaving the groove and passing onto the forearm, it follows under the aponeurotic arch of the flexor digitorum ulnaris (m. flexor carpi ulnaris) as part of the humero-ulnar arcade. Distally it pierces this muscle in the so-called cubital tunnel, where it can be compressed.
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