MSK 4c: radioulnar joints

Question 1

Location of proximal radioulnar joint

Answer 1

Between head of radius and radial notch of ulna

Radial head held in position by the anular ligament of the radius

Question 2

What type of joints are the radioulnar joints?

Answer 2

Synovial pivot joints

Question 3

Joint capsule of proximal RUJ?

Answer 3

Fibrous layer is continuous with elbow capsule

Synovial membrane lines non-articulating aspects

Question 4

Describe the anular ligament

Answer 4

A strong ring encircling the radial head in the PRUJ

Allows the radius to rotate without stretching or tearing the synovial membrane

Question 5

What vessels pass through the PRUJ?

Answer 5

Radial portion of the peri-articular arterial anastomoses
Median nerve (pronation)
Musculocutaneous and radial nerves (supination)

Question 6

Describe the movements of the PRUJ

Answer 6

PRONATION: pronator quadratus + pronator teres, assistance from flexor carpi radialis, palmaris longus and brachioradialis

SUPINATION: supinator, biceps brachii, some EPL and ECRL

Question 7

How do the radius and ulnar articulate at the PRUJ?

Answer 7

Head of radius pivots on capitulum (part of humerus.

Pronation and supination almost always accompanied by synergistic movements of the shoulder and elbow

Question 8

What is the difference between subluxation and dislocation?

Answer 8

Dislocation: complete loss of contact of joint surfaces
Subluxation: partial dislocation so that the bone ends are misaligned but still in contact

Question 9

What is pulled elbow and why is it common in children?

Answer 9

Head of radius subluxates from the anular ligament

Anular ligament still quite lax as not fully developed in children

Question 10

What is the interosseous joint?

Answer 10

Fibrous joint of connective tissue containing small holes for forearm vasculature
Fibres run infero-medially allowing distribution of force from radius to ulnar
Holds radius and ulnar together in pronation and supination, site of attachment for forearm muscles, transfers forces from radius to ulnar

Question 11

Describe the articulations of the distal radioulnar joint

Answer 11

Rounded head of ulna articulates with the ulnar notch on the medial side of the distal radisu
L-shaped joint cavity (coronal section)
Fibrocartilage triangular articular disc binds the end of the ulna and radius

Question 12

Describe the joint capsule of the DRUJ

Answer 12

Fibrous layer encloses except superiorly
Synovial membrane extends to form the sacciform recess of the DRUJ to accommodate twisting of the capsule during pronation

Question 13

Which vessels pass through the DRUJ?

Answer 13

Anterior and posterior interosseous arteries and nerves

Question 14

Describe the movements at the DRUJ

Answer 14

Pronation: distal end of radius rotates anteriorly and medially to cross the ulna
Supination: radius uncrosse from ulna, distal end rotates laterally