Introduction

The radius is one of two large bones in the forearm. It is located laterally and extends from the elbow to the wrist.

The elbow articulates in 4 places:

  1. Elbow – with the capitulum of the humerus
  2. Proximal radioulnar joint
  3. Distal radioulnar joint
  4. Wrist – with the scaphoid and lunate (proximal carpal bones)

Proximal Radius

The main parts of the proximal radius are the head, the neck and the radial tuberosity.

  • Head: articulates with the capitulum of the humerus. Medially it articulates with the radial notch of the ulna
  • Neck: narrowing of the radius between the head the the radial tuberosity
  • Radial tuberosity: projects medially from the radius just below the neck. Roughened surface where the biceps brachii inserts.

Shaft

The shaft of the radius is roughly triangular in cross section with 3 borders and 3 surfaces. It is narrow proximally and broader distally.

Borders

  1. Anterior (volar)
  2. Posterior (dorsal)
  3. Interosseus

Surfaces

  1. Anterior (volar)
  2. Posterior (dorsal)
  3. Lateral

Several muscles attach to the surfaces of the radius. The surfaces are generally smooth, other than a roughened area on the lateral surface of the radius, which serves as the site for the attachment of the pronator teres.

Distal Radius

There are two facets at the distal end of the radius which articulate with the scaphoid and the lunate.

The lateral margin of the radius extends distally as the radial styloid process.

The medial aspect of the distal radius has a notch, the ulnar notch, for articulating with the ulna at the distal radioulnar joint.