MSK upper Limb anatomy

Question 1

What are the primary actions of the deltoid muscle?

Answer 1

Action
= Abduction of the arm (15-90°), shoulder flexion, and extension

Innervates
= Axillary nerve

Clinical Relevance
= Weakness with axillary nerve injury
= shoulder dislocation
= surgical neck fracture

Question 2

What is the function of the Supraspinatus muscle?

Answer 2

Action
= Initiates arm abduction (0–15°)

Innervates
= suprascapular nerve

Clinical Relevance
= Commonly torn in rotator cuff injuries

Question 3

What is the function of the infraspinatus muscle?

Answer 3

Action
= External rotation of the shoulder

Innervates
= Suprascapular nerve

Clinical Relevance
= Weak external rotation with suprascapular nerve injury
= rotator cuff tear)

Question 4

What is the function of the teres minor muscle?

Answer 4

Action
= External rotation of the shoulder

Innervates
= Axillary nerve

Clinical Relevance
= Rarely injured in isolation

Question 5

What is the function of the subscapularis muscle?

Answer 5

Action
= Internal rotation of the shoulder

Innervates
= Upper and lower subscapular nerves

Clinical Relevance
= Weak internal rotation with subscapular nerve injury

Question 6

What are the primary functions of the biceps brachii?

Answer 6

Action
= Elbow flexion, supination, and shoulder flexion

Innervates
= Musculocutaneous nerve

Clinical Relevance
= Weakness in elbow flexion and supination with musculocutaneous nerve injury

Question 7

What is the function of the Brachialis?

Answer 7

Action
= Pure elbow flexion

Innervates
= Musculocutaneous nerve (with some radial)

Clinical Relevance
= Main elbow flexor. Often spared in nerve injury due to dual innervation

Question 8

What is the main action of the triceps brachii?

Answer 8

Action
= Elbow extension

Innervates
= Radial nerve

Clinical Relevance
= Weakness in elbow extension with radial nerve injury

Question 9

What is the primary function of the flexor carpi radialis?

Answer 9

Action
= Wrist flexion and radial deviation

Innervates
= Median nerve

Clinical Relevance
= Weakness in wrist flexion with median nerve injury

Question 10

What is the function of the Extensor Carpi Radialis Longus/Brevis?

Answer 10

Action
= Wrist extension, radial deviation

Innervates
= Radial nerve

Clinical Relevance
= Weakness → wrist drop

Question 11

What is the function of the snuffbox/thumb muscles?

Answer 11

Abductor Pollicis Longus
Extensor Pollicis Brevis
Extensor Pollicis Longus

Action
= Abduction (APL) and extension of thumb

Innervates
= Radial nerve

Clinical Relevance
= De Quervain’s tenosynovitis

Question 12

What is the function of the thenar Muscles of the hand?

Answer 12

Abductor Pollicis Brevis
Flexor Pollicis Brevis
Opponens Pollicis

Action
= important for thumb movements

Innervates
= Median nerve (except for the deep head of flexor pollicis brevis, which is innervated by the ulnar nerve)

Clinical Relevance
= carpal tunnel syndrome

Question 13

This patient presents with a shoulder dislocation what muscles are affected?

Answer 13

axillary nerve → deltoid

Question 13

This patient presents with wrist drop what muscles are affected?

Answer 13

radial nerve → extensors

Question 13

This patient presents with carpal tunnel what muscles are affected?

Answer 13

thenar wasting → median nerve

Question 14

Pin on the anatomical snuffbox
(1) Name one structure that passes through this region

(2) What are the muscles forming its borders?

Answer 14

(1) Radial artery

(2) Abductor pollicis longus + Extensor pollicis brevis (lateral)

Extensor pollicis longus (medial)

Question 15

Empty Can Test is used for what?

Answer 15

Supraspinatus (rotator cuff tear)