Muscles of the forearm

Question 1

What are the two joints of the forearm and what are their functions?

Answer 1

Synovial hinge joint (elbow) –> flexion/extension

Synovial pivot joint (proximal radioulnar) –> supination / pronation.

Question 2

What are the ligaments around the elbow joint and what are their functions?

Answer 2

Radial collateral ligament, ulnar collateral ligament,
annular ligament
Stabilise / strengthen joint

Question 3

What are the muscles of the anterior compartment of the forearm?

Answer 3

Mainly flexors
Superficial -> 3 flexors of wrist (carpi), 1 pronator
Intermediate -> 1 flexor of digits 2-5 (digitorum)
Deep -> 1 flexor of digits 2-5 (digitorum), 1 flexor of thumb (pollicis), 1 pronator.
(Superficial + intermediate from common flexor origin)

Question 4

What are the muscles of the superficial layer of the anterior compartment?

Answer 4

Pronator teres: insertion -> radius
Flexor carpi radialis: insertion -> base of 2nd + 3rd metacarpal.
Palmaris longus: insertion -> palmar aponeurosis
Flexor carpi ulnaris: origin -> medial epicondyle, insertion -> pisiform, hook of hamate, base of 5th metacarpal.

Question 5

What is the clinical significance of the superficial layer of muscles?

Answer 5

Golfers elbow / medial epicondylitis -> inflammation of tendons at CFO due to overuse/excessive gripping

Question 6

What is the muscle of the intermediate layer and what is its origin, insertion and action?

Answer 6

Flexor digitorum superficialis
Origin: common flexor origin
Insertion: base of middle phalanx of digits 2,3,4,5
Action: flexes wrist, metacarpal phalangeal joint (knuckles) + proximal interphalangeal joint.

Question 7

What is the origin, insertion and action of the flexor digitorum profundus and which layer is it found in?

Answer 7

Deep
Origin: ulna + interosseous membrane
Insertion: distal phalynx of digits 2, 3, 4, 5
Action: flexes wrist, metacarpophalangeal joints at digit 2,3,4, 5 + proximal and distal interphalangeal joints.

Question 8

What is the origin, insertion and action of the flexor pollicis longus and which layer is it found in?

Answer 8

Deep
Origin: radius + interosseous membrane
Insertion: distal phalynx of thumb.
Action: flexes thumb.

Question 9

What is the remaining muscle of the deep layer?

Answer 9

Pronator quadratus

Question 10

What are the muscles of the posterior compartment of the forearm?

Answer 10

Mainly extensors
Superficial muscles -> 3 extensors of wrist (carpi), 1 extensor of digits 2-5 (digitorum), 1 accessory extensor to digit 5 (digiti minimi), brachioradialis + anconeus.
Deep muscles -> 2 extensors of thumb (pollicis), 1 abductor of thumb (pollicis), 1 accessory extensor to digit 2 (indicis), 1 supinator.

Question 11

What are the muscles of the superficial layer and what is their origin?

Answer 11

Extensor carpi radialis longus/brevis 
Extensor digitorum 
Extensor digiti minimi (accessory to extensor digitorum) 
Extensor carpi ulnaris 
Common extensor origin

Question 12

What is the clinical significance of the superficial layer?

Answer 12

Tennis elbow / lateral epicondylitis -> inflammation of tendons at CEO due to overuse/forceful extension

Question 13

What is the origin, insertion and action of the extensor carpi radialis longus and brevis?

Answer 13

Longus
Origin: supracondylar ridge 
Insertion: base of 2nd metacarpal 
Brevis 
Origin: common extensor origin
Insertion: base of 3rd metacarpal. 
Action: extends wrist

Question 14

What is the origin, insertion and action of the extensor digitorum?

Answer 14

Origin: common extensor origin.
Insertion of the 4 tendons: middle phalynx of digits 2,3,4, 5 + distal phalynx of digit 2,3.4, 5.
Action: extends wrist, metacarpophalangeal joint 2 to 5 + proximal and distal interphalangeal joint digits 2 to 5.

Question 15

What is the origin, insertion and action of the extensor carpi ulnaris?

Answer 15

Origin: common extensor origin
Insertion: base of 5th metacarpal
Action: extends wrist

Question 16

What are the two other superficial muscles of the posterior compartment?

Answer 16

Brachioradialis
Action: flexor when half pronated 
Anconeus
Origin: lateral epicondyle 
Insertion: olecranon of ulna
Action: stabilises elbow

Question 17

What are the muscles of the deep layer of the posterior compartment?

Answer 17

Supinator
Extensor indicis (accessory to extensor digitorum)
Anatomical snuff box:
Abductor pollicis longus
Extensor pollicis brevis
Extensor pollicis longus

Question 18

Which muscles perform wrist abduction and adduction?

Answer 18

Abduction (radial deviation) -> flexor carpi radialis,
extensor carpi radialis (longus + brevis).
Adduction (ulnar deviation) -> flexor carpi ulnaris, extensor carpi ulnaris.
Splints wrist to allow fine movements of hand

Question 19

Which muscles are involved in supination?

Answer 19

Biceps brachii
Supinator:
Origin: superficial head from lateral epicondyle + deep head from ulna.
Insertion: proximal shaft of radius.

Question 20

Which muscles are involved in pronation?

Answer 20

Pronator teres has humeral + ulnar heads
Insertion: radius  
Pronator quadratus
Origin: ulna
Insertion: radius

Question 21

What is the position of the radius and ulna during pronation and supination?

Answer 21

During pronation -> radius rotates over ulna

During supination -> radius + ulna are parallel

Question 22

What is the purpose of the flexor retinaculum?

Answer 22

Transverse carpal ligament

Prevents bowing of tendons, separates tendons into compartments.

Question 23

What is the carpal tunnel and what are its contents?

Answer 23

Tunnel for flexor tendons to digits + median nerve.
Median nerve
Flexor policis longus
Flexor digitorum superficialis
Flexor digitorum profundus
Synovial sheaths

Question 24

What are the insertions to the long tendons?

Answer 24

Tendons to digits 2 – 5
Extensor digitorum into middle + distal phalanx
Flexor digitorum superficialis into middle phalanx
Flexor digitorum profundus into distal phalanx