The Radioulnar Joints Flashcards
What are the radioulnar joints?
Two locations in which the radius and ulna articulate in the forearm
Both of these joints are classified as pivot joints, responsible for pronation and supination of the forearm.
Name the two radioulnar joints
Proximal radioulnar joint
Distal radioulnar joint
Describe the proximal radioulnar joint
This is located immediately distal to the elbow joint, and is enclosed within the same articular capsule. It’s an articulation between the head of the radius and the radial notch of the ulna
Describe the distal radioulnar joint
This is located just proximally to the wrist, and is an articulation between the ulnar notch of the radius and the ulnar head
In the proximal radioulnar joint, what holds the radial head in place?
The radial head is held in place by the annular radial ligament, which forms a collar around the joint. The annular radial ligament is lined with a synovial membrane, reducing friction during movement.
Describe the movement produced at the proximal radioulnar joint
Movement is produced by the head of the radius rotating within the annular ligament. There are two movements possible at this joint; supination and pronation.
Which muscles produce pronation at the proximal radioulnar joint?
Pronator quadratus
Pronator teres
Name the innervations of the pronators of the forearm
Pronator quadratus - anterior interosseous nerve
Pronator teres - median nerve
Which muscles produce supination at the proximal radioulnar joint?
Supinator
Biceps Brachii
Name the innervations of the supinators of the forearm
Supinator - deep branch of radial nerve
Biceps brachii - Musculocutaenous nerve
Name the origin and insertion of Pronator quadratus
Origin - anterior surface of distal ulna
Insertion - anterior surface of distal radius
Name the origin and insertion of Pronator teres
Origin - humeral head - medial epicondyle of humerus via common flexor tendon - ulnar head - coronoid process of ulna
Insertion - middle part of lateral surface of radius
Name the origin and insertion of Supinator
Origin - lateral epicondyle of humerus, supinator crest of ulna, annular ligament of radius
Insertion - Anterior, lateral and posterior surfaces of proximal third of radius
Name the origin and insertion of Biceps brachii
Origin - short head - coracoid process, long head - supraglenoid tubercle
Insertion - radial tuberosity, fascia of forearm via bicipital aponeurosis
What helps to strengthen the distal radioulnar joint?
In addition to anterior and posterior ligaments strengthening the joint, there is also a fibrocartilaginous ligament present called the articular disk.
What are the functions of the articular disk?
- Binds the radius and ulna together, and holds them together during movement at the joint
- Separates the distal radioulnar joint from the wrist joint
What type of joint is the distal radioulnar joint?
Like the proximal radioulnar joint, this is a pivot joint, allowing for pronation and supination. The ulnar notch of the radius slides anteriorly over the head of the ulnar during such movements
Which muscles produce pronation?
Pronator quadratus
Pronator teres
Which muscles produce supination?
Biceps brachii
Supinator
What is the interosseous membrane?
Sheet of connective tissue that joins the radius and ulna together between the radioulnar joints
Why are there small holes in the sheet of the interosseous membrane?
To allow the forearm vasculature to pass through
What is the function of the interosseous membrane?
- Holds the radius and ulna together during pronation and supination of the forearm, providing additional stability
- Acts as a site of attachment for muscles in the anterior and posterior compartments of the forearm
- Transfers forces from the radius to the ulna
