MSK Muscles of the forearm

Question 1

List the muscles in the superficial, intermediate and deep compartment of the anterior forearm

Answer 1

Superficial: PFPF
Pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris

Intermediate:
Flexor digitorum superficialis

Deep:
Flexor digitorum profundus, flexor pollicis longus, pronator quadratus

Question 2

What is the generalised function of the muscles in the anterior compartment of the forearm?

Answer 2

Flexion at the wrist and fingers

Pronation

Question 3

Superficial

What are the attachments and actions of the pronator teres?

Answer 3

Lateral border forms medial border of cubital fossa

Originates from the medial epicondyle of the humerus and coronoid process of ulna
Attaches to mid shaft of radius

Actions:
Pronates forearm

Question 4

Superficial

What are the attachments and actions of the flexor carpi radials?

Answer 4

Originates from medial epicondyle and attaches to metacarpals 2 and 3

Actions:
Flexion and abduction of the wrist

Question 5

Superficial

What are the attachments and actions of the palmaris longus?

Answer 5

(absent in ~15% of the population) Just distal to wrist you will find median nerve directly underneath it

Originates from medial epicondyle and attaches to flexor retinaculum of wrist

Actions:
Flexion at the wrist

Question 6

Superficial

What are the attachments and actions of the flexor carpi ulnaris?

Answer 6

Originates from medial epicondyle as well as a long origin from the ulna, attaches to pisiform

Actions:
Flexes and adducts wrist

Question 7

What is the innervation of the superficial muscles of the anterior forearm?

Answer 7

All median nerve except flexor carpi ULNARIS which is ulnar nerve

Question 8

Intermediate

What are the attachments and actions of the flexor digitorum superficialis?

Answer 8

Good landmark - the median nerve and ulnar artery pass between its 2 heads

Originates from medial epicondyle and radius, splits into 4 tendons at wrist, travel through carpal tunnel and attach to middle phalanges of 4 fingers

Actions:
Flexes wrist, flexes MCP and proximal IP joints of 4 fingers

Question 9

What innervates the flexor digitorum superficialis?

Answer 9

Median nerve

Question 10

Deep

What are the attachments and actions of the flexor digitorum profundus?

Answer 10

Originates from ulna, splits into 4 tendons at wrist, travel through carpal tunnel and attach to distal phalanges of 4 fingers

Actions:
Flexes wrist, flexes MCP and ONLY MUSCLE that can flex distal IP joints of 4 fingers

Question 11

Deep

What are the attachments and actions of the flexor pollicis longus?

Answer 11

Lateral to flexor digitorum profundus
Originates from anterior radius and attaches to distal phalanx of thumb

Actions:
Flexes IP and MCP joint of the thumb

Question 12

Deep

What are the attachments and actions of the pronator quadratus?

Answer 12

Square shaped muscle, deepest

Originates from anterior ulna and attaches to anterior radius

Actions:
Pronates forearm

Question 13

What innervates the deep muscles of the anterior forearm>?

Answer 13

Anterior interosseous branch of median nerve
(medial half of flexor digitorum profundus which acts on pinky and ring innervated by ulnar nerve)

Clinical note: as the flexor digitorum profundus is the only muscle that can flex the distal IP joints, you can use it to test the function of the median nerve (index and middle) and ulnar (pinky and ring)

Question 14

List the muscles in the deep and superficial compartments of the posterior forearm

Answer 14

Superficial:
Brachioradialis, extensor carpi radialis longus and brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, anconeus

Deep:
Supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, extendor indicis proprius

Question 15

What is the generalised function of the muscles in the anterior compartment of the forearm?

Answer 15

Extension of the wrist and fingers

Question 16

Superficial

What are the attachments and actions of the brachioradialis?

Answer 16

Exception - its origin and innervation are common to extensor muscles, however it is an elbow flexor

Originates from lateral supraepicondylar ridge and attaches to distal radius, just before styloid process.

Actions:
flexes the elbow

Question 17

Superficial

What are the attachments and actions of the extensor carpi radialis longus and brevis?

Answer 17

Lateral forearm

The longus originates from the supracondylar ridge and brevis originates from the lateral epicondyle. Their tendons attach to metacarpals 2 and 3

Actions:
Extends and abducts wrist

Question 18

Superficial

What are the attachments and actions of the extensor digitorum?

Answer 18

Main extensor of fingers - to test forearm is pronated and fingers extended against resistance

Originates from lateral epicondyle, and tendon splits into 4 at distal forearm and attaches to extensor hood of each finger

Actions:
Extends 4 fingers at IP and MCP joints

Question 19

Superficial

What are the attachments and actions of the extensor digiti minimi?

Answer 19

Originates from lateral epicondyle and attaches with extensor digitorum tendon into extensor hood of little finger

Actions:
Extends little finger and contributes to wrist extension

Question 20

Superficial

What are the attachments and actions of the extensor carpi ulnaris?

Answer 20

Originates from lateral epicondyle and attaches to base of metacarpal 5

Actions:
Extension and adduction of wrist

Question 21

Superficial

What are the attachments and actions of the anconeus?

Answer 21

(blended with fibres of the triceps so the muscles can be indistinguishable)

Originates from lateral epicondyle and attaches to posterior lateral olecrannon

Actions:
Moves ulna during pronation and extends elbow

Question 22

What is the innervation of all the posterior forearm muscles?

Answer 22

Radial nerve

Question 23

What is tennis elbow?

Answer 23

Lateral epicondylitis - inflammation of periosteum of the lateral epicondyle. Onset usually 40-50yrs
Causes by repeated use of superficial extensor muscles which strains their common tendinous attachment to the lateral epicondyle

Question 24

Deep

What are the attachments and actions of the supinator?

Answer 24

Makes up the floor of the cubital fossa, has 2 heads which the radial nerve passes between

Originates from lateral epicondyle and posterior ulna, inserts together on the posterior radius

Actions:
Supinates forearm

Question 25

Deep

What are the attachments and actions of the abductor pollicis longus?

Answer 25

Immediately distal to supinator
Tendon contributes lateral border of the anatomical snuffbox

Originates from the interosseous membrane and posterior surfaces of radius and ulna, attaches to lateral base of metacarpal 1

Actions;
Abducts thumb

Question 26

Deep

What are the attachments and actions of the extensor policis brevis?

Answer 26

Medial and deep to abductor pollicis longus, tendon contributes to lateral border of snuffbox

Originates from posterior radius and interosseous membrane, attach to base of proximal phalanx of thumb

Actions:
Extends MCP and carpometacarpal joints of thumb

Question 27

Deep

What are the attachments and actions of the extensor policis longus?

Answer 27

The tendon forms medial border of anatomical snuffbox

Originates from posterior ulna and interosseous membrane, attaches to distal phalanx of the thumb

Extends all joints of the thumb

Question 28

Deep

What are the attachments and actions of the extensor indicis proprius?

Answer 28

Allows index to extend independently of other fingers

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

Actions:
Extends index finger

Question 29

What happens when there is radial nerve damage proximal to the elbow and what are the common sites of damage?

Answer 29

Can be damaged in the axilla by humeral dislocations or fractures
Can be damaged in the radial groove of humerus by humeral shaft fracture

The radial nerve innervates all extensor muscles in the forearm so if it is damages there is wrist drop - tone of flexor muscles produces unopposed flexion