Radius and ulna: Anterior view (English)

The radius is the shorter of the two bones of the forearm and consists of a proximal extremity, shaft and a distal extremity. The proximal end of radius consists of a head and neck. The discoid head of the radius articulates superiorly with the capitulum of the humerus, contributing to the formation of the elbow joint. At the same time, the head of the radius also articulates with the ulna forming the proximal radioulnar joint. In this joint, the circumference of the head of the radius is situated on the radial notch of ulna. The neck of radius is a narrowing of the radius that lies just distal to the head. Distal to the medial aspect of the neck is an oval bony protrusion known as the radial tuberosity, onto which the biceps brachii inserts. The shaft of the radius acts as an important attachment point for muscles of the forearm, some of which include the supinator and pronator teres muscles. From this anterior view, the anterior border of the shaft of the radius can be appreciated. The distal extremity of the radius widens to form three smooth, concave surfaces. The medial aspect of the distal radius forms a concavity known as the ulnar notch, which articulates with the distal ulna. The lateral aspect of the distal radius forms a ridge and terminates distally as the radial styloid process. The ulna is similarly composed of a proximal end, shaft and distal end. The proximal end of the ulna is particularly wide to accommodate the trochlea of humerus. Projecting anteriorly from the proximal portion of the ulna is the coronoid process. The coronoid process aids in stabilizing the elbow joint and preventing hyperflexion of the forearm. Inferior to the coronoid process is the tuberosity of ulna, which functions as an attachment point for the brachialis muscle. The distal end of the ulna tapers to form the disc-like head of the ulna. The head of the ulna does not articulate with the carpal bones and is therefore not a component of the wrist joint. Projecting from the head of the ulna is a small bony protrusion known as the styloid process of ulna.