The Radius

The radius is a long bone, located laterally in the forearm. The upper end is narrow, but the lower section is wide. The shaft is convex laterally and the interosseous membrane is related to the medial sharp border.

The Upper end

The head is disc-shaped and articulates with the capitulum of the humerus superiorly and with the radial notch of the ulna medially to form the superior radioulnar joint. The neck lies just under the head and has a medial projection called radial tuberosity (bicipital tuberosity).

                                                               Figure1: Radius

The anterior border of the shaft extends from the radial tuberosity to the styloid process anteriorly and the posterior border extends from the posterior part of the radial tuberosity to the styloid process. The sharpest of the three borders is the medial border which is related to the interosseous membrane. The lower end of the radius is the widest part and contains grooves for the extensor tendons on its posterior surface.  The ulnar notch is located on its medial surface, while the styloid process lies on its lateral. The inferior surface articulates with the scaphoid and lunate to form the wrist joint.

                                               Figure2: Anterior attachment of the radius and ulna

The muscles attachment to the radius

1) Biceps is inserted into the posterior part of the radial tuberosity. 
2) Three muscles are attached to the anterior surface of the radius: flexor digitorum superficialis, flexor pollicis longus and pronator quadratus. 
3) Supinator, pronator teres and brachioradialis are inserted in the lateral surface of the radius. 
4) Abductor pollicis longus and extensor pollicis brevis both originate from the posterior surface of the radius.

 

                                               Figure3: Posterior attachment of the radius and ulna

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