Learning Objectives
By the end of this section, you should be able to:
- Identify the proximal and distal radioulnar joints and their articulations.
- Describe the ligaments and stabilising structures of each joint.
- Explain how pronation and supination occur at the radioulnar joints.
- Describe the role of the interosseous membrane.
- Recognise common fracture–dislocation patterns involving the radius and ulna.
Overview
The radioulnar joints are the two sites at which the radius and ulna articulate in the forearm:
- Proximal radioulnar joint – located near the elbow; formed between the head of the radius and the radial notch of the ulna.
- Distal radioulnar joint – located near the wrist; formed between the ulnar notch of the radius and the head of the ulna.
Both joints are pivot-type synovial joints and together allow pronation and supination of the forearm. In this section, we will review the anatomy, movements, stabilising structures, and clinical relevance of the radioulnar joints.
Proximal Radioulnar Joint
The proximal radioulnar joint lies immediately distal to the elbow joint and shares the same joint capsule. It is formed by an articulation between the radial head and the radial notch of the ulna.
The radial head is stabilised by the annular ligament, which forms a collar around it and holds it against the ulna. The inner surface of this ligament is lined with synovial membrane, reducing friction during movement.
Movements
Rotation of the radial head within the annular ligament produces:
- Pronation – pronator teres, pronator quadratus
- Supination – supinator, biceps brachii
Distal Radioulnar Joint
The distal radioulnar joint is located just proximal to the wrist. It is formed by an articulation between the ulnar notch of the radius and the ulnar head.
It is supported by anterior and posterior radioulnar ligaments and a fibrocartilaginous articular disc, which:
- Binds the radius and ulna together during rotation.
- Separates the distal radioulnar joint from the wrist joint.
During pronation and supination, the ulnar notch of the radius glides over the ulnar head.
Movements
- Pronation – pronator teres, pronator quadratus
- Supination – supinator, biceps brachii
Interosseous Membrane
The interosseous membrane spans between the medial border of the radius and the lateral border of the ulna. Small openings allow the passage of forearm vessels.
Functions
- Stabilises the radius and ulna
- Provides muscle attachments
- Transfers forces from the radius to the ulna.
Clinical Relevance
Fracture–Dislocation Patterns
The radius and ulna function as a ring structure—a break in one part is usually accompanied by injury elsewhere.
- Monteggia fracture – proximal ulna fracture with radial head dislocation.
- Galeazzi fracture – distal radius fracture with ulnar head dislocation.
