Radius: Landmarks, Articulations and Muscle Attachments

By Dr Richard Miller, MBChB FRCS · Reviewed 1 October 2026

The radius is the lateral bone of the forearm, running from the elbow to the thumb side of the wrist. It is narrow at the elbow and broad at the wrist, rotates around the ulna in pronation and supination, and carries most of the load from the hand to the forearm.

Radius · key facts

Type: Long bone, lateral bone of the forearm
Articulations: Capitulum of humerus, ulna (proximal and distal radioulnar joints), scaphoid and lunate
Key landmarks: Head, neck, radial tuberosity, interosseous border, dorsal tubercle, styloid process, ulnar notch
Muscle attachments: Biceps, supinator, pronator teres, FDS, FPL, pronator quadratus, brachioradialis, APL, EPB
Ossification: Primary centre in the shaft; secondary centres at the head and distal end

3D model of the radius: radius — 3D model showing the radius.BodyParts3D, © The Database Center for Life Science licensed under CC Attribution 4.0 International

Structure

The radius has a small proximal end, a shaft that curves laterally, and a large distal end that forms most of the wrist joint.

Proximal end

Head: a disc with a shallow cup (fovea) on top for the capitulum of the humerus. Its rim, the articular circumference, turns within the annular ligament and against the radial notch of the ulna.
Neck: the narrow segment below the head.
Radial tuberosity: a rough bump on the medial side just below the neck, where the biceps tendon inserts.

Shaft

The shaft is triangular in cross-section, with anterior, posterior and lateral surfaces. Its sharp medial edge, the interosseous border, gives attachment to the interosseous membrane, whose fibres run downwards and medially to the ulna so that force from the hand passes to the ulna and on to the humerus. The shaft bows laterally, and this curve is needed for the radius to swing around the ulna in pronation.

Distal end

Styloid process: projects distally on the lateral side and reaches further distally than the ulnar styloid.
Ulnar notch: a concave facet on the medial side for the head of the ulna.
Dorsal (Lister's) tubercle: a ridge on the back that acts as a pulley for the EPL tendon.
Carpal articular surface: divided by a low ridge into a lateral facet for the scaphoid and a medial facet for the lunate.

Articulations and muscle attachments

The radius takes part in four joints: the humeroradial part of the elbow, the proximal and distal radioulnar joints, and the radiocarpal (wrist) joint. The ulna is separated from the carpus by the articular disc of the triangular fibrocartilage complex, so the radius is the main bone of the wrist joint.

Site	Muscle
Radial tuberosity	Biceps brachii
Proximal lateral and anterior shaft	Supinator, wrapping around the neck and upper shaft
Middle of lateral surface (point of greatest convexity)	Pronator teres
Anterior oblique line	Flexor digitorum superficialis (radial head)
Anterior surface, middle part	Flexor pollicis longus
Distal anterior surface	Pronator quadratus
Base of styloid process	Brachioradialis
Posterior surface	Abductor pollicis longus, extensor pollicis brevis

Ossification

The radius ossifies from a primary centre in the shaft, which appears in the embryonic period, and from secondary centres at each end. The distal centre appears early in childhood and the head centre appears later. The distal end is the growing end of the radius: it contributes most of the bone's length and fuses last, in late adolescence. This is why distal radial physeal (Salter–Harris) injuries in children are common and can disturb growth.

Clinical relevance

The radius fractures more often than any other forearm bone, and the pattern depends on where it breaks and which way the fragment moves.

Colles' fracture: a distal radius fracture with dorsal displacement and angulation of the distal fragment, giving the dinner-fork deformity. It typically follows a fall on the outstretched hand in older adults with osteoporosis.
Smith's fracture: the reverse, with volar displacement, often after a fall on the back of the flexed wrist.
Barton's fracture: an intra-articular fracture of the dorsal or volar rim with subluxation of the carpus.
Radial head fracture: follows a fall on the outstretched hand, with pain over the lateral elbow and loss of rotation.
Pulled elbow: in young children the radial head slips partly out of the annular ligament after a sudden pull on the arm.
Galeazzi fracture: a radial shaft fracture with dislocation of the distal radioulnar joint.

The deep branch of the radial nerve, the posterior interosseous nerve, winds around the neck of the radius within supinator. It can be injured in radial neck fractures and during surgical approaches to the proximal radius, causing finger and thumb drop without sensory loss.

How it is examined

On a cadaveric spotter, in an OSPE and in MRCS Part B anatomy.

On a bone tray, orient the radius by its head (a flat disc at the narrow end) and its broad distal end with a lateral styloid. The ulna has the hooked olecranon at its large proximal end.
Side the radius by placing the dorsal tubercle posteriorly and the styloid laterally. The ulnar notch faces medially.
A pin on the rough bump below the neck is the radial tuberosity for biceps. A pin on the rough area mid-lateral shaft is the pronator teres insertion.
Expect a follow-up linking a landmark to a nerve: the posterior interosseous nerve winds around the radial neck in supinator.
Examiners like the difference between Colles' (dorsal displacement) and Smith's (volar displacement), and between Galeazzi (radius) and Monteggia (ulna).

Key points

The radius is the lateral forearm bone: narrow at the elbow, broad at the wrist.
The head rotates within the annular ligament against the radial notch of the ulna.
Biceps inserts on the radial tuberosity; pronator teres on the middle of the lateral shaft.
The distal radius articulates with the scaphoid and lunate and forms most of the wrist joint.
The distal physis is the growing end and fuses last.
Colles', Smith's, Barton's and Galeazzi fractures all involve the radius.

Common questions

Is the radius on the thumb side?

Yes. In the anatomical position, with the palms facing forwards, the radius is the lateral bone of the forearm and lies on the thumb side. Its styloid process can be felt at the base of the thumb, and it forms most of the wrist joint. The ulna is the medial bone, on the little finger side, and forms most of the elbow joint.

What attaches to the radial tuberosity?

The tendon of biceps brachii attaches to the radial tuberosity, the rough prominence on the medial side of the radius just below the neck. Because the tuberosity turns posteriorly in pronation, biceps unwinds the radius when it contracts, making it the most powerful supinator of the forearm, particularly with the elbow flexed. A bursa separates the tendon from the front of the tuberosity.

What is a Colles' fracture?

A Colles' fracture is a fracture of the distal radius, within a few centimetres of the wrist, in which the distal fragment is displaced and tilted dorsally. The wrist takes on a dinner-fork deformity when viewed from the side. It usually follows a fall on the outstretched hand, most often in older adults with osteoporotic bone, and the ulnar styloid may also break.

Which bones does the radius articulate with?

The radius articulates with the humerus, the ulna, the scaphoid and the lunate. The head meets the capitulum of the humerus at the elbow. The radius meets the ulna at the proximal and distal radioulnar joints, allowing pronation and supination. Its distal end articulates with the scaphoid and lunate at the wrist, forming the radiocarpal joint.

References

Gray's Anatomy: The Anatomical Basis of Clinical Practice. Standring S (ed). Elsevier. 42nd edition, 2020.
Moore's Clinically Oriented Anatomy. Moore KL, Dalley AF, Agur AMR. Wolters Kluwer. 9th edition, 2022.
McMinn and Abrahams' Clinical Atlas of Human Anatomy. Elsevier.