Muscles of the Shoulder and Arm

Authors

Affiliations

Nate Yomogida, PT, DPT

Doctor of Physical Therapy

B.S. in Kinesiology

Chloë Kerstein, PT, DPT

Doctor of Physical Therapy

B.A. in Neuroscience

Deltoid Muscles

Table 1: Deltoid muscles

Muscle	Origin	Insertion	Innervation	Action
Anterior deltoid	Lateral third of clavicle	Deltoid tuberosity of humerus	Axillary n. C5 - C6	GHJ: Flexion, IR, Adduction
Lateral deltoid	Acromion	Deltoid tuberosity of humerus	Axillary n. C5 - C6	GHJ: Abduction
Posterior deltoid	Scapular spine	Deltoid tuberosity of humerus	Axillary n. C5 - C6	GHJ: Extension, ER, Abduction

Rotator Cuff

Table 2: Rotator Cuff

Muscle	Origin	Insertion	Innervation	Action
Infraspinatus	Infraspinous Fossa of Scapula	Greater tubercle of Humerus	Suprascapular n. C4 - C6	GHJ: ER, Stabilization
Subscapularis	Subscapular fossa	Lesser tubercle of Humerus	Upper Subscapular n. Lower Subscapular n. C5 - C6	GHJ: IR, Stabilization
Supraspinatus	Supraspinous Fossa of scapula	Greater tubercle of Humerus	Suprascapular n. C4 - C6	GHJ: Initiates abduction, Stabilization
Teres minor		Greater tubercle of Humerus	Axillary n. C5 - C6	GHJ: ER, Weak adduction

Pectoral Girdle

Table 3: Pectoral Girdle Muscles

Muscle	Origin	Insertion	Innervation	Action
Coracobrachialis	Coracoid process	Humerus (in line with crest of lesser tubercle)	Musculocutaneous n. C5 - C7	GHJ: Flexion, Adduction, IR
Pectoralis major	Clavicle (medial half) Sternum Costal cartilages 1-6 Rectus sheath (anterior layer)	Humerus (crest of greater tubercle)	Lateral pectoral n. Medial pectoral n. C5 - T1	Entire muscle: Adduction, IR Clavicular & Sternocostal parts: Flexion, Aids in respiration when shoulder is fixed
Pectoralis minor	3-5 ribs	Coracoid process	Medial pectoral n. C8 - T1	Scapula: Depression, Downward rotation, Protraction Respiration: Assists in respiration
Subclavius	1st rib	Clavicle (inferior surface)	N. to subclavius C5 - C6	SCJ: Stabilization