Posterior Forearm Muscles

Question 1

What nerve innervates all the posterior muscles of the forearm?

Answer 1

Radial nerve

Question 2

Name the 7 muscles found in the superior posterior compartment of the forearm

Answer 2

Brachioradialis 
Extensor carpi radialis longus 
Extensor carpi radialis brevis 
Extensor digitorum
Extensor digiti minimi 
Extensor carpi ulnaris 
Anconeus

Question 3

What are the attachments of the brachioradialis?

Answer 3

Originates from the proximal aspect of the lateral supracondylar ridge of humerus

Attaches to the distal end of the radius (just before the radial styloid process)

Question 4

What is the action of the bracioradialis muscle of the superior posterior compartment of the forearm?

Answer 4

Flexion at the elbow

Question 5

What nerve innervates the brachioradialis muscle of the superior posterior compartment of the forearm?

Answer 5

Radial nerve

Question 6

What are the attachments of the extensor carpi radialis longus (ECRL/ECRB)?

Answer 6

ECRL- originates from the lateral supracondylar ridge
ECRB- originates from the lateral epicondyle

Both attach to metacarpal bones 2 and 3

Question 7

What is the action of the extensor carpi radialis longus muscle of the superior posterior compartment of the forearm?

Answer 7

Extends and abducts the wrist

Question 8

What is the action of the extensor carpi radialis brevis muscle of the superior posterior compartment of the forearm?

Answer 8

Extends and abducts the wrist

Question 9

What nerve innervates the extensor carpi radialis longus and brevis muscles of the superior posterior compartment of the forearm?

Answer 9

Radial nerve

Question 10

What are the attachments of the extensor digitorum?

Answer 10

Originates from the lateral epicondyle

Splits into 4 tendons which insert into the extensor hood of each finger

Question 11

What are the actions of the extensor digitorum muscle of the superior posterior compartment of the forearm?

Answer 11

Extends medial four fingers at the MCP and IP joints

Question 12

What nerve innervates the extensor digitorum muscle of the superior posterior compartment of the forearm?

Answer 12

Deep branch of the radial nerve

Question 13

In some people what two muscles of the superior posterior compartment of the forearm are fused?

Answer 13

Extensor digitorum

Extensor digiti minimi

Question 14

What are the attachments of the digiti minimi muscle of the superior posterior compartment of the forearm?

Answer 14

Originates form the lateral epicondyle of the humerus

Attaches to the extensor hood of the little finger (with extensor digitorum)

Question 15

What is the action of the digiti minimi muscle of the superior posterior compartment of the forearm?

Answer 15

Extends the little finger and contributes to extension at the wrist

Question 16

What nerve innervates the digiti minimi muscle of the superior posterior compartment of the forearm?

Answer 16

Deep branch of the radial nerve

Question 17

What are the attachments of the extensor carpi ulnaris muscle of the superior posterior compartment of the forearm?

Answer 17

Originates from the lateral epicondyle

Attaches to the base of metacarpal V

Question 18

What is the action of the extensor carpi ulnaris muscle of the superior posterior compartment of the forearm?

Answer 18

Extension and adduction of wrist

Question 19

What nerve innervates the extensor carpi ulnaris muscle of the superior posterior compartment of the forearm?

Answer 19

Radial nerve (deep branch)

Question 20

What muscle is blended with the fibres of the triceps brachii?

Answer 20

Anconeus

Question 21

What are the attachments of the anconeus muscle of the superior posterior compartment of the forearm?

Answer 21

Originates from the lateral epicondyle

Attaches to the posterior and lateral part of the olecranon

Question 22

What is the action of the anconeus muscle of the superior posterior compartment of the forearm?

Answer 22

Extends and stabilises the elbow joint

Abducts the ulna during pronation of the forearm

Question 23

What nerve innervates the anconeus muscle of the superior posterior compartment of the forearm?

Answer 23

Radial nerve

Question 24

What is the medical term for tennis elbow?

Answer 24

Lateral epicondylitis

Question 25

What is tennis elbow?

Answer 25

Inflammation of the periosteum if the lateral epicondyle *peak age of onset is 40-50 years old

Question 26

What causes tennis elbow?

Answer 26

Repeated use of the superficial extensor muscles which strain their common tendinous attachment to the lateral epicondyle

Question 27

What is special about the supinator muscle of the deep posterior compartment of the forearm?

Answer 27

It is the floor of the cubital fossa Two heads which the deep branch of the radial nerve passes between

Question 28

What are the attachments of the supinator muscle of the deep posterior compartment of the forearm?

Answer 28

Two heads: 1. Originates from the lateral epicondyle of the humerus 2. Originates from the posterior surface of the ulna Insert together into the posterior surface of the radius

Question 29

What is the action of the supinator muscle of the deep posterior compartment of the forearm?

Answer 29

Supinate the forearm

Question 30

What nerve innervates the supinator muscle of the deep posterior compartment of the forearm?

Answer 30

Radial nerve (deep branch)

Question 31

What are the attachments of the abductor pollicis longus muscle of the deep posterior compartment of the forearm?

Answer 31

Originates from the interosseous membrane and the adjacent posterior surfaces of the radius and ulna Attcahes to the lateral side of the base of metacarpal 1

Question 32

What is special about the abductor pollicis longus muscle of the deep posterior compartment of the forearm?

Answer 32

Its tendon contributes to the lateral border of the anatomical snuffbox

Question 33

What is the action of the abductor pollicis longus muscle of the deep posterior compartment of the forearm?

Answer 33

Abducts the thumb

Question 34

What nerve innervates the abductor pollicis longus muscle of the deep posterior compartment of the forearm?

Answer 34

Radial nerve (deep branch)

Question 35

Where can the extensor pollicis brevis be found?

Answer 35

Medially and deep to the abductor pollicis longus

Question 36

What is special about the extensor pollicis brevis muscle of the deep posterior compartment of the forearm?

Answer 36

Its tendon contributes to the lateral border of the anatomical snuffbox

Question 37

What are the attachments of the extensor pollicis brevis muscle of the deep posterior compartment of the forearm?

Answer 37

Originates from the posterior surface of the radius and interosseous membrane Attaches to the proximal phalanx of the thumb

Question 38

What is the action of the extensor pollicis brevis muscle of the deep posterior compartment of the forearm?

Answer 38

Extends at the MCP and carpometacarpal joints of the thumb

Question 39

What nerve innervates the extensor pollicis brevis muscle of the deep posterior compartment of the forearm?

Answer 39

Radial nerve (posterior interosseous branch)

Question 40

What is special about the extensor pollicis longus muscle of the deep posterior compartment of the forearm?

Answer 40

Its tendon forms the medial border of the anatomical snuffbox in the hand

Question 41

What are the attachments of the extensor pollicis longus muscle of the deep posterior compartment of the forearm?

Answer 41

Originates from the posterior surface of the ulna and interosseous membrane Attaches to the distal phalanx of the thumb

Question 42

What is the action of extensor pollicis longus muscle of the deep posterior compartment of the forearm?

Answer 42

Extends all joints of the thumb: carpometacarpal, metacarpophalangeal and interphalangeal

Question 43

What is the innervation of the extensor pollicis longus muscle of the deep posterior compartment of the forearm?

Answer 43

Radial nerve (posterior interosseous branch)

Question 44

Why is the extensor indices proprius muscle of the deep posterior compartment of the forearm important?

Answer 44

Becase it allows the index finger to be independent of the other fingers during extension

Question 45

What are the attachments of the extensor indicis propius muscle of the deep posterior compartment of the forearm?

Answer 45

Originates from the posterior surface of the ulna and interosseous membrane (distal to the extensor pollicis longus) Attaches to the extensor hood of the index finger

Question 46

What is the action of the extensor indicis proprius muscle of the deep posterior compartment of the forearm?

Answer 46

Extends the index finger

Question 47

What nerve innervates the extensor indicis proprius muscle of the deep posterior compartment of the forearm?

Answer 47

Radial nerve (posterior interosseous branch)

Question 48

What is a sign of radial nerve injury that has occurred proximal to the elbow?

Answer 48

Wrist drop

Question 49

What are the two common site that the radial nerve could be damaged in and how?

Answer 49

Axilla: injured via humeral dislocations of fractures of the proximal humerus Radial groove: injured via humeral shaft fracture

Question 50

In the event of radial nerve lesions, what muscles are paralysed?

Answer 50

Those in the extensor compartment (posterior forearm)

Question 51

Why does radial nerve injury lead to wrist drop?

Answer 51

Because the extensors are no longer working so the flexor muscles are unopposed and the wrist is held in flexion