Joints - Radioulnar Joints (RUJ)

Question 1

How many RUJs are there?

Answer 1

There are two:

1) Proximal radioulnar joint (PRUJ)
2) Distral radioulnar joint (DRUJ)

Question 2

What are the articulations in the RUJs?

Answer 2

PRUJ - between the head of the radius and the radial notch of the ulna.

DRUJ - between the ulnar notch of the radius and the ulnar head.

Question 3

What are the features (location, ligaments and movement) of PRUJ?

Answer 3

Located immediatly distal to the elbow and enclosed in the same articular capsule.

Ligaments:

Anular ligament - forms a collar around the joint and is lined with synovial membrane to reduce friction.

Movement:

Produced by the radial head rotating around within the annular ligament.

1) Pronation - pronator quadratus and pronator teres.
2) Supination - supinator and biceps brachii

Question 4

What are the features (location, ligaments, movemet) of DRUJ?

Answer 4

Located just proximally to the wrist joint.

Ligaments:

Anterior and posterior ligaments strengthening the joint.

Articular disc - bind the ulna and radius together and holds them together during movement of the joint. It also separates the DRUJ from the wrist joint.

Movement:

Pronation - pronator quadratus and pronator teres

Supination - supinator and biceps brachii

Question 5

What is the interosseous membrane?

Answer 5

This is a sheet of connective tissue that joins the radius and ulna between the radioulnar joints. Spans between the medial radial border and the lateral ulnar border.

There are small holes to allow as a conduit for the forearm vasculature.

Question 6

What are the functions of the interosseous membrane?

Answer 6

1) Holds the radius and ulna together - during pronation and supination of the forearm, providing additional stability.
2) Acts as a site of attachment - for muscles in the anterior and posterior compartments of the forearm.
3) Transfers forces from the radius to the ulna.

Question 7

Clinical relevance: fractures to the radius and ulna

Answer 7

Although the radius and ulna are two separate bone, they can be thought as a ring when dealing with injuries.

There are two classical fractures:

1) Monteggia’s fracture - usually caused by a force from behind the ulna. The proximal shaft of ulna is fractured, and the head of the radius dislocates at the distal radio-ulnar joint.
2) Galeazzi’s fracture - a fracture to the distal radiusm with the ulna head dislocation at the distal radioulnar joint.