Shoulder Muscles Chapter 5

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).

Anterior Muscles Coracobrachialis Pectoralis major Subscapularis

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

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

Pectoralis Major

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

Superior Muscles Deltoid Supraspinatus

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

Deltoid Lateral view

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

Inferior Muscles Latissimus dorsi Teres major

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

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

Posterior Muscles Infraspinatus Teres minor

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

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

Rotator Cuff Muscles S.I.T.S

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

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

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

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

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

Name the abductor muscles deltoid (all fibers) supraspinatus

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