Learning Objectives
By the end of this section, you should be able to:
- Describe the anatomical position and function of the radius
- Identify the major bony landmarks of the proximal, shaft, and distal radius
- Explain the articulations of the radius at the elbow, forearm, and wrist
- Recognize common clinical fractures involving the radius
The radius is a long bone of the forearm that lies laterally and parallel to the ulna. It is the mobile bone of the forearm, pivoting around the ulna during pronation and supination at the proximal and distal radioulnar joints.
Articulations of the Radius
The radius participates in four joints:
- Elbow joint – head of radius with the capitulum of the humerus
- Proximal radioulnar joint – head of radius with the radial notch of the ulna
- Wrist joint – distal radius with the scaphoid and lunate
- Distal radioulnar joint – ulnar notch of the radius with the head of the ulna
Proximal Radius
The proximal end contributes to both the elbow and proximal radioulnar joints.
Key Landmarks
-
Head of radius
Disk-shaped with a concave superior surface for the capitulum.
Its medial rim articulates with the radial notch of the ulna. -
Neck
A narrow region just below the head. -
Radial tuberosity
A roughened projection for attachment of the biceps brachii tendon.
Shaft of the Radius
The shaft is triangular with three borders and three surfaces and widens distally.
- On the lateral surface, a rough area provides attachment for the pronator teres.
- The interosseous border serves as an attachment for the interosseous membrane.
Distal Radius
The distal radius is broad and rectangular.
Key Features
- Styloid process – a lateral projection palpable at the wrist
- Ulnar notch – a medial concavity that articulates with the head of the ulna
- Carpal facets – inferior surface articulates with:
- Scaphoid
- Lunate
These form the radiocarpal (wrist) joint.
Clinical Relevance: Common Radius Fractures
Colles’ Fracture
- Most common radial fracture
- Fall on an outstretched hand
- The distal fragment is displaced posteriorly
- Produces the “dinner fork” deformity
Smith’s Fracture
- Fall onto the back of the hand
- The distal fragment is displaced anteriorly
- Reverse of Colles’ fracture
Radial Head Fracture
- Due to a FOOSH injury
- Radial head driven into the capitulum
Paired Forearm Injuries
Because the radius and ulna are joined by the interosseous membrane, force can be transmitted between them.
- Monteggia fracture
Fracture of the proximal ulna with anterior dislocation of the radial head - Galeazzi fracture
Fracture of the distal radius with dislocation of the ulna head at the wrist
