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The humeroulnar joint (ulnohumeral or trochlear joint [1]) is part of the elbow-joint. It is composed of two bones, the humerus and ulna, and is the junction between the trochlear notch of ulna and the trochlea of humerus. [1] It is classified as a simple hinge-joint, which allows for movements of flexion, extension and circumduction.
The elbow is the region between the upper arm and the forearm that surrounds the elbow joint. [1] The elbow includes prominent landmarks such as the olecranon , the cubital fossa (also called the chelidon, or the elbow pit), and the lateral and the medial epicondyles of the humerus .
The head of the radius has a cylindrical form, and on its upper surface is a shallow cup or fovea for articulation with the capitulum of the humerus. The circumference of the head is smooth; it is broad medially where it articulates with the radial notch of the ulna, narrow in the rest of its extent, which is embraced by the annular ligament. [1]
The trochlear notch (/ ˈ t r ɒ k l ɪər /), [1] also known as semilunar notch and greater sigmoid cavity, is a large depression in the upper extremity of the ulna that fits the trochlea of the humerus (the bone directly above the ulna in the arm) as part of the elbow joint. It is formed by the olecranon and the coronoid process.
The arm proper (brachium), sometimes called the upper arm, [5] the region between the shoulder and the elbow, is composed of the humerus with the elbow joint at its distal end. The elbow joint is a complex of three joints — the humeroradial, humeroulnar, and superior radioulnar joints — the former two allowing flexion and extension whilst ...
During elbow flexion, the vertical anterior part of the trochlea keeps the upper arm and forearm aligned (when viewed in front). During elbow extension, however, the oblique posterior part makes contact with the trochlear notch on the ulna so that this obliquity forces the main axis of the forearm to form a small angle with that of the upper arm.
Joint From To Description 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 a ball-and-socket joint. Superior radioulnar joint: head of the radius: radial notch of the ulna
The proximal radioulnar joint is a synovial pivot joint. [1] It occurs between the circumference of the head of the radius and the ring formed by the radial notch of the ulna and the annular ligament. [2] The interosseous membrane of the forearm and the annular ligament stabilise the joint. [2]