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The distal radioulnar articulation [1] (also known as the distal radioulnar joint, [2] or inferior radioulnar joint [1] [3]) is a synovial pivot joint between the two bones in the forearm; the radius and ulna. It is one of two joints between the radius and ulna, the other being the proximal radioulnar articulation.
The radius is a long bone, prism-shaped and slightly curved longitudinally. The radius is part of two joints: the elbow and the wrist. At the elbow, it joins with the capitulum of the humerus, and in a separate region, with the ulna at the radial notch. At the wrist, the radius forms a joint with the ulna bone.
The ulna forms part of the wrist joint and elbow joints. Specifically, the ulna joins (articulates) with: trochlea of the humerus, at the right side elbow as a hinge joint with semilunar trochlear notch of the ulna. the radius, near the elbow as a pivot joint, this allows the radius to cross over the ulna in pronation.
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]
The interosseous membrane of the forearm (rarely middle or intermediate radioulnar joint) is a fibrous sheet that connects the interosseous margins of the radius and the ulna. It is the main part of the radio-ulnar syndesmosis , a fibrous joint between the two bones.
The annular ligament binds the head of the radius to the radial notch of the ulna, preventing any separation of the two bones laterally.Therefore, the humeroradial joint is not functionally a ball and socket joint, although the joint surface in itself allows movement in all directions.
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.
The elbow joint is a hinge joint between the arm and the forearm; [2] more specifically between the humerus in the upper arm and the radius and ulna in the forearm which allows the forearm and hand to be moved towards and away from the body.