The radius and ulna are two parallel bones found in the forearm.

The radius and ulna (Credit: OpenStax, CC BY-SA 4.0)

Description

In an anatomical presentation (when the hands are extended and the palm is facing the viewer) the radius is lateral and the ulna is medial.

They are inverse in measures, resulting from the position of the head: the radius is small proximally (head) and large distally, while the ulna is large proximally and small distally (head).

These two bones articulate with the humerus at the elbow joint and with the carpal bones at the wrist joint. They can be divided into proximal ends, middle parts, and distal ends.

Proximal ends

Radius

The proximal end of the radius consists of:

  • The head, a thick disc-shaped structure with a concave circular superior surface that articulates with the capitulum. Medially, it articulates with the radial notch on the proximal end of the ulna.
  • The neck, a short and narrow cylinder of bone that lies between the previous and following structure of the radius.
  • The radial tuberosity, a large blunt

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