The Radioulnar Joints

Question 1

What are the radioulnar joints?

Answer 1

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.

Question 2

Name the two radioulnar joints

Answer 2

Proximal radioulnar joint

Distal radioulnar joint

Question 3

Describe the proximal radioulnar joint

Answer 3

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

Question 4

Describe the distal radioulnar joint

Answer 4

This is located just proximally to the wrist, and is an articulation between the ulnar notch of the radius and the ulnar head

Question 5

In the proximal radioulnar joint, what holds the radial head in place?

Answer 5

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.

Question 6

Describe the movement produced at the proximal radioulnar joint

Answer 6

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.

Question 7

Which muscles produce pronation at the proximal radioulnar joint?

Answer 7

Pronator quadratus

Pronator teres

Question 8

Name the innervations of the pronators of the forearm

Answer 8

Pronator quadratus - anterior interosseous nerve

Pronator teres - median nerve

Question 9

Which muscles produce supination at the proximal radioulnar joint?

Answer 9

Supinator

Biceps Brachii

Question 10

Name the innervations of the supinators of the forearm

Answer 10

Supinator - deep branch of radial nerve

Biceps brachii - Musculocutaenous nerve

Question 11

Name the origin and insertion of Pronator quadratus

Answer 11

Origin - anterior surface of distal ulna

Insertion - anterior surface of distal radius

Question 12

Name the origin and insertion of Pronator teres

Answer 12

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

Question 13

Name the origin and insertion of Supinator

Answer 13

Origin - lateral epicondyle of humerus, supinator crest of ulna, annular ligament of radius
Insertion - Anterior, lateral and posterior surfaces of proximal third of radius

Question 14

Name the origin and insertion of Biceps brachii

Answer 14

Origin - short head - coracoid process, long head - supraglenoid tubercle
Insertion - radial tuberosity, fascia of forearm via bicipital aponeurosis

Question 15

What helps to strengthen the distal radioulnar joint?

Answer 15

In addition to anterior and posterior ligaments strengthening the joint, there is also a fibrocartilaginous ligament present called the articular disk.

Question 16

What are the functions of the articular disk?

Answer 16

• Binds the radius and ulna together, and holds them together during movement at the joint
• Separates the distal radioulnar joint from the wrist joint

Question 17

What type of joint is the distal radioulnar joint?

Answer 17

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

Question 18

Which muscles produce pronation?

Answer 18

Pronator quadratus

Pronator teres

Question 19

Which muscles produce supination?

Answer 19

Biceps brachii

Supinator

Question 20

What is the interosseous membrane?

Answer 20

Sheet of connective tissue that joins the radius and ulna together between the radioulnar joints

Question 21

Why are there small holes in the sheet of the interosseous membrane?

Answer 21

To allow the forearm vasculature to pass through

Question 22

What is the function of the interosseous membrane?

Answer 22

• 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