MOB TCD

Superior and Inferior Radioulnar Joint

Professor Emeritus Moira O’Brien

FRCPI, FFSEM, FFSEM (UK), FTCD

Trinity College

Dublin

Supination

• Supination is when the bones of forearm are parallel

• Palm of hand is facing anteriorly• Supination with the elbow flexed is

a more powerful movement than pronation

MOB TCD

• Radius crosses the ulnar• Palm of the hand is facing posteriorly• Radial styloid is more distal than ulnar

styloid• The axis of rotation passes through the

middle of the head of the radius to the base of the styloid process of the ulna

Pronation MOB TCD

• Three joints• Superior radioulnar joint• Interosseous membrane• Inferior radioulnar joint• Axis of rotation• Middle of head of radius• Base of styloid process of ulnar

Supination and Pronation MOB TCD

Superior Radioulnar Joint

• Synovial pivot joint• Circumference of head of radius• Radial notch of ulnar• Annular ligament covered with

articular cartilage• Quadrate membrane• Capsular ligament• Articular surfaces hyaline

cartilage• Synovial membrane continuous

with elbow joint

MOB TCD

• Annular ligament attached to

anterior and posterior borders of radial notch

• Lateral ligament of elbow to upper margin

• Annular ligament covered with articular cartilage

Superior Radioulnar Joint MOB TCD

• Capsule is attached• Lower border of the annular

ligament• Neck of radius• Ulnar below the radial notch

Superior Radioulnar Joint MOB TCD

• Quadrate membrane• Lower margin of the radial notch

ulnar• Neck of radius• Synovial membrane• Lines capsule, non-articular

structures• Continuous above the annular

ligament with synovial membrane of elbow

Superior Radioulnar Joint MOB TCD

Interosseous Membrane

• Syndesmosis• Fibres pass mainly

downwards and medially

• Radius to ulna• Extends origins of

muscles• Pierced by anterior

interosseous artery• Transmits force

from radius to ulna

MOB TCD

Interosseous Membrane MOB TCD

• Radial styloid is more distal than ulnar

• Synovial pivot joint• L-shaped ulnar

notch of radius• Lateral and distal

aspect of head of ulna

• Triangular fibro- cartilaginous disc

Superior Radioulnar Joint MOB TCD

• Radial styloid process is more distal than ulnar styloid process

Inferior Radioulnar Joint MOB TCD

• Synovial pivot • L-shaped• Medial and distal aspect of

head of ulna• Ulnar notch of radius• Triangular cartilaginous disc

Inferior Radioulnar Joint MOB TCD

• Articular surfaces• Hyaline cartilage• Capsule just beyond articular

margins• Synovial membrane lines

capsule and non-articular structures

• Radial styloid process is more distal than ulnar styloid process

Inferior Radioulnar Joint MOB TCD

Supinators: Biceps Brachii and Supinator

• Biceps brachii with the elbow flexed

• More powerful• Musculocutaneous C5,6• Supinator (two heads) with

elbow extended• Posterior interosseous C5,6

MOB TCD

• Supinator has two heads of origin• The superficial head arises from

the lateral epicondyle of the humerus, the lateral ligament of the elbow and the annular ligament

• The deep head arises from the supinator crest and supinator fossa of the ulna

Supinator MOB TCD

Supinator

• Supinator is inserted into the upper third of the outer surface of the radius

• When the elbow is extended• The supinator muscle supinates

the forearm i.e. it rotates the radius to turn the palm anteriorly

• Supplied by the posterior interosseous nerve C6,7, which passes between the two heads

MOB TCD

• Arises from two heads• The common flexor origin • The medial margin of the coranoid

process of the ulna

Pronator Teres MOB TCD

Pronator Teres

• It is inserted into the most convex aspect of the shaft of the radius

• The radial artery passes superficial to the two heads

• The ulnar artery deep to the two heads• The median nerve between the two

heads• Its action is to assist pronator quadratus

in rapid or forceful pronation of the forearm

• It is also a weak flexor of the elbow• Median nerve C6

MOB TCD

• Arises from the anterior aspect of the distal portion of the ulna

• Inserted into the distal aspect of the radius• It is a pronator of the forearm• Supplied by the anterior interosseous

branch of the median nerve• The pronator quadratus is the prime mover

in pronation • Pronator teres contracts when further

speed or strength is required

Pronator Quadratus MOB TCD

• Arises from the upper third of the lateral supracondylar line of the humerus

• Inserted into the distal aspect of the radius • Radial nerve C5,6• Flexor of elbow• In the mid position it can initiate, either

pronation or supination• It is used, for example, in the back cast

when fly-fishing

Brachioradialis MOB TCD

• Slipped radial epiphysis

Radial Epiphysis MOB TCD

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