1. Shoulder Muscles
Chapter 5

2. Determination of Muscle Action
Muscle location?
Origin and insertion
What joint(s) it crosses or act on?
Where does the muscle cross the joint? (e.g. anterior, lateral, etc.)
What are the possible planes of movement and actions at that joint? (also see pages 23, 24)
What is the line of pull?
Muscles only pull on bones, they do not push bones.
Insertion is usually pulled towards the origin.
Remember, most muscle can not perform opposite actions (e.g. flexion AND extension).

3. Anterior Muscles
Coracobrachialis
Pectoralis major
Subscapularis

4. Coracobrachialis Origin: coracoid process Insertion: medial humerus
Actions:
Horizontal Adduction of the shoulder
flexion of the shoulder
adduction of the shoulder

6. Pectoralis Major Origin: Proximal clavical (clavicular head)
Sternum (sternal head)
Insertion: Intertubercular groove
Actions:
Clavicular (upper)
Internal rotation
Horizontal adduction
Flexion up to 60º
Adduction beyond 90º
Abduction below 90º
Sternal (lower)
Extension to a neutral position
Adduction

7. Pectoralis Major

8. Subscapularis Origin: subscapular fossa Insertion: lesser tubercle
Actions:
Internal rotation
Adduction
Extension
Other: anterior rotator cuff muscle
Note: Anterior view. The ribs are
removed from this image

10. Superior Muscles
Deltoid
Supraspinatus

11. Deltoid Origin: Anterior: distal clavicle Middle: acromion process
Posterior: spine of scapula
Insertion:
Actions
Anterior: abduction, flexion, internal rotation, horizontal adduction
Middle: abduction
Posterior: abduction, extension, external rotation, horizontal abduction

12. Deltoid
Lateral view

13. Supraspinatus Origin: supraspinatus fossa Insertion: greater tubercle
Action: abduction
Other: rotator cuff muscle

15. Inferior Muscles
Latissimus dorsi
Teres major

16. Latissimus Dorsi Origin: Insertion: intertubercular groove Actions:
adduction
internal rotation
extension
horizontal abduction
“swimmer’s muscle”

18. Teres Major Origin: inferior angle Insertion: intertubercular groove
Actions:
adduction
internal rotation
extension
“lats little helper”

20. Posterior Muscles
Infraspinatus
Teres minor

21. Infraspinatus Origin: infraspinus fossa Insertion: greater tubercle
Actions:
extension
external rotation
horizontal abduction
Other: rotator cuff muscle

23. Teres Minor Origin: lateral border Insertion: greater tubercle
Actions:
extension
external rotation
horizontal abduction
Other: rotator cuff

25. Rotator Cuff Muscles
S.I.T.S

27. Name the horizontal adduction muscles
pectoralis major (upper and lower fibers)
corachobrachialis
anterior deltoid

28. Name the horizontal abduction muscles
posterior deltoid
infraspinatus
teres minor
latissimus dorsi

29. Name the flexor muscles
coracobrachialis
pect major (upper fibers)
anterior deltoid

30. Name the extensor muscles
latissimus dorsi
teres major
posterior deltoid
pectoralis major (lower fibers)

31. Name the adductor muscles
pect major (upper and lower fibers)
coracobrachialis
latissimus dorsi
teres major

32. Name the abductor muscles
deltoid (all fibers)
supraspinatus

33. Name the internal rotator muscles
subscapularis
latissimus dorsi
teres major
anterior deltoid