Lower extremity of radius

Bone: Distal radius
The radius and ulna of the left forearm, posterior surface. The top is proximal (elbow) and bottom is distal (wrist).
Gray's	subject #52 220

The distal end of the radius is large and of quadrilateral form.

Articular surfaces

It is provided with two articular surfaces - one below, for the carpus, and another at the medial side, for the ulna.

• The carpal articular surface is triangular, concave, smooth, and divided by a slight antero-posterior ridge into two parts. Of these, the lateral, triangular, articulates with the scaphoid bone; the medial, quadrilateral, with the lunate bone.

• The articular surface for the ulna is called the ulnar notch (sigmoid cavity) of the radius; it is narrow, concave, smooth, and articulates with the head of the ulna.

These two articular surfaces are separated by a prominent ridge, to which the base of the triangular articular disk is attached; this disk separates the wrist-joint from the distal radioulnar articulation.

Non-articular surfaces

This end of the bone has three non-articular surfaces - volar, dorsal, and lateral.

• The volar surface, rough and irregular, affords attachment to the volar radiocarpal ligament.

• The dorsal surface is convex, affords attachment to the dorsal radiocarpal ligament, and is marked by three grooves. Enumerated from the lateral side:
  • The first groove is broad, but shallow, and subdivided into two by a slight ridge; the lateral of these two transmits the tendon of the extensor carpi radialis longus muscle, the medial the tendon of the extensor carpi radialis brevis muscle.
  • The second is deep but narrow, and bounded laterally by a sharply defined ridge; it is directed obliquely from above downward and lateralward, and transmits the tendon of the extensor pollicis longus muscle.
  • The third is broad, for the passage of the tendons of the Extensor indicis proprius and Extensor digitorum communis.

• The lateral surface is prolonged obliquely downward into a strong, conical projection, the styloid process, which gives attachment by its base to the tendon of the brachioradialis, and by its apex to the radial collateral ligament of the wrist-joint. The lateral surface of this process is marked by a flat groove, for the tendons of the abductor pollicis longus muscle and extensor pollicis brevis muscle.

Additional images

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  Ligaments of wrist. Anterior view.

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  Ligaments of wrist. Posterior view.

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  Vertical section through the articulations at the wrist, showing the synovial cavities.

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  Transverse section across distal ends of radius and ulna.

• Radius 10deg lateral break gnangarra.jpg

  X-Ray of a closed fracture of the distal radius with 10^o of lateral angulation, subject is the left arm of 11 year old male

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.