Anatomy of Shoulder and Arm Muscles: Origins, Insertions, and Actions

Supraspinatus

Origin: Supraspinous fossa of scapula

Insertion: Greater tubercle of humerus (superior facet

Action: Abducts arm (first 15°); stabilizes glenohumeral joint

Infraspinatus

Origin: Infraspinous fossa of scapula

Insertion: Greater tubercle of humerus (middle facet)

Action: Laterally rotates arm; stabilizes shoulder joint

Teres Minor

Origin: Lateral border of scapula (upper 2/3)

Insertion: Greater tubercle of humerus (inferior facet)

Action: Laterally rotates and adducts arm; stabilizes shoulder joint

Subscapularis

Origin: Subscapular fossa of scapula

Insertion: Lesser tubercle of humerus

Action: Medially rotates arm; stabilizes shoulder joint

Teres Major

Origin: Inferior angle of scapula (posterior surface)

Insertion: Medial lip of intertubercular sulcus of humerus

Action: Adducts, extends, and medially rotates arm

Deltoid

Origin: Lateral third of clavicle, acromion, spine of scapula

Insertion: Deltoid tuberosity of humerus

Action: Anterior fibers: flex and medially rotate arm; Middle fibers: abduct arm; Posterior fibers: extend and laterally rotate arm

Coracobrachialis

Origin: Coracoid process of scapula

Insertion: Medial surface of humerus (mid-shaft)

Action: Flexes and adducts arm at shoulder joint

Triceps Brachii (Long Head)

Origin: Infraglenoid tubercle of scapula

Insertion: Olecranon process of ulna

Action: Extends forearm; long head also extends and adducts arm

Triceps Brachii (Lateral Head)

Origin: Posterior surface of humerus (above radial groove)

Insertion: Olecranon process of ulna

Action: Extends forearm

Triceps Brachii (Medial Head)

Origin: Posterior surface of humerus (below radial groove)

Insertion: Olecranon process of ulna

Action: Extends forearm

Anconeus

Origin: Lateral epicondyle of humerus

Insertion: Lateral aspect of olecranon and superior ulna

Action:Assists triceps in forearm extension; stabilizes elbow

Biceps Brachii (Long Head)

Origin: Supraglenoid tubercle of scapula

Insertion: Radial tuberosity and bicipital aponeurosis

Action: Flexes forearm; supinates forearm; assists in shoulder flexion

Biceps Brachii (Short Head)

Origin: Coracoid process of scapula

Insertion: Radial tuberosity and bicipital aponeurosis

Action: Flexes and supinates forearm; assists in shoulder flexion

Brachialis

Origin: Distal anterior surface of humerus

Insertion: Coronoid process and ulnar tuberosity

Action: Primary flexor of forearm

Brachioradialis

Origin: Lateral supracondylar ridge of humerus

Insertion: Styloid process of radius

Action: Flexes forearm (especially when forearm is mid-pronated)

Pronator Teres

Origin: Medial epicondyle of humerus (common flexor tendon) and coronoid process of ulna

Insertion: Mid-lateral surface of radius

Action: Pronates forearm; assists in flexion at elbow

Flexor Carpi Radialis

Origin: Medial epicondyle of humerus

Insertion: Base of 2nd and 3rd metacarpals

Action: Flexes and abducts hand at wrist

Palmaris Longus

Origin: Medial epicondyle of humerus

Insertion: Palmar aponeurosis

Action: Flexes hand at wrist; tenses palmar fascia

Flexor Carpi Ulnaris

Origin: Medial epicondyle of humerus and olecranon of ulna

Insertion: Pisiform, hook of hamate, base of 5th metacarpal

Action: Flexes and adducts hand at wrist

Flexor Digitorum Superficialis

Origin: Medial epicondyle of humerus, coronoid process of ulna, and anterior radius

Insertion: Middle phalanges of digits 2-5

Action: Flexes proximal interphalangeal (PIP) and metacarpophalangeal (MCP) joints of digits 2-5; flexes wrist

Flexor Digitorum Profundus

Origin: Anteromedial surface of ulna and interosseous membrane

Insertion: Bases of distal phalanges of digits 2-5

Action: Flexes distal interphalangeal (DIP) joints; assists in wrist flexion

Extensor Carpi Radialis Longus

Origin: Lateral supracondylar ridge of humerus

Insertion: Base of 2nd metacarpal

Action: Extends and abducts hand at wrist

Extensor Carpi Radialis Brevis

Origin: Lateral epicondyle of humerus

Insertion: Base of 3rd metacarpal

Action: Extends and assists in abduction of hand at wrist

Extensor Digitorum

Origin: Lateral epicondyle of humerus

Insertion: Extensor expansions of digits 2-5

Action: Extends fingers and hand at wrist

Extensor Carpi Ulnaris

Origin: Lateral epicondyle of humerus and posterior ulna

Insertion: Base of 5th metacarpal

Action: Extends and adducts hand at wrist

Supinator

Origin: Lateral epicondyle of humerus, radial collateral ligament, annular ligament, supinator crest of ulna

Insertion: Lateral and anterior surface of proximal radius

Action: Supinates forearm

Flexor Pollicis Longus

Origin: Anterior surface of radius and interosseous membrane

Insertion: Base of distal phalanx of thumb

Action: Flexes thumb (IP and MCP joints)

Extensor Pollicis Longus

Origin: Posterior surface of ulna and interosseous membrane

Insertion: Base of distal phalanx of thumb

Action: Extends thumb at IP, MCP, and CMC joints

Extensor Pollicis Brevis

Origin: Posterior surface of radius and interosseous membrane

Insertion: Base of proximal phalanx of thumb

Action: Extends thumb at MCP and CMC joints

Abductor Pollicis Longus

Origin: Posterior surface of ulna, radius, and interosseous membrane

Insertion: Base of 1st metacarpal

Action: Abducts and extends thumb at CMC joint