Radius bone

 The radius

The radius is a long bone in the forearm. It lies laterally and parallel to ulna, the second of the forearm bones. The radius pivots around the ulna to produce movement at the proximal and distal radio-ulnar joints.

The radius articulates in four places:

• Elbow joint – Partly formed by an articulation between the head of the radius, and the capitulum of the humerus.

• Proximal radioulnar joint – An articulation between the radial head, and the radial notch of the ulna.

• Wrist joint – An articulation between the distal end of the radius and the carpal bones.

• Distal radioulnar joint – An articulation between the ulnar notch and the head of the ulna.

Proximal Region of the Radius

The proximal end of the radius articulates in both the elbow and proximal radioulnar joints.

Important bony landmarks include the head, neck and radial tuberosity:

• Head of radius – A disk shaped structure, with a concave articulating surface. It is thicker medially, where it takes part in the proximal radioulnar joint.

• Neck – A narrow area of bone, which lies between the radial head and radial tuberosity.

• Radial tuberosity – A bony projection, which serves as the place of attachment of the biceps brachii muscle.

Shaft of the Radius

The radial shaft expands in diameter as it moves distally. Much like the ulna, it is triangular in shape, with three borders and three surfaces.

In the middle of the lateral surface, there is a small roughening for the attachment of the pronator teres muscle.

Distal Region of the Radius

In the distal region, the radial shaft expands to form a rectangular end. The lateral side projects distally as the styloid process. In the medial surface, there is a concavity, called the ulnar notch, which articulates with the head of ulna, forming the distal radioulnar joint.

The distal surface of the radius has two facets, for articulation with the scaphoid and lunate carpal bones. This makes up the wrist joint.


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