Extrinsic Muscles of the Wrist, Fingers, and Thumb

Flexor Carpi Radialis

Origin: Medial epicondyle of humerus. Insertion: Bases of 2nd and 3rd metacarpals. Action: Wrist flexion and radial deviation.

Flexor Carpi Ulnaris

Origin: Medial epicondyle of humerus, olecranon and posterior ulna. Insertion: Pisiform, hook of hamate and base of 5th metacarpal. Action: Wrist flexion and ulnar deviation.

Palmaris Longus

Origin: Medial epicondyle of humerus. Insertion: Flexor retinaculum and palmar aponeurosis. Action: Weak wrist flexion and tightening palmar fascia.

Flexor Digitorum Superficialis

Origin: Medial epicondyle, coronoid process of ulna and anterior radius. Insertion: Middle phalanges of digits 2–5. Action: Flexes proximal interphalangeal joints; assists MCP and wrist flexion.

Flexor Digitorum Profundus

Origin: Proximal anterior and medial ulna and interosseous membrane. Insertion: Distal phalanges of digits 2–5. Action: Flexes distal interphalangeal joints; assists finger and wrist flexion.

Flexor Pollicis Longus

Origin: Anterior radius and interosseous membrane. Insertion: Base of distal phalanx of thumb. Action: Flexes thumb, especially interphalangeal joint.

Extensor Carpi Radialis Longus

Origin: Lateral supracondylar ridge of humerus. Insertion: Base of 2nd metacarpal. Action: Wrist extension and radial deviation.

Extensor Carpi Radialis Brevis

Origin: Lateral epicondyle of humerus. Insertion: Base of 3rd metacarpal. Action: Wrist extension and radial deviation.

Extensor Carpi Ulnaris

Origin: Lateral epicondyle of humerus and posterior ulna. Insertion: Base of 5th metacarpal. Action: Wrist extension and ulnar deviation.

Extensor Digitorum

Origin: Lateral epicondyle of humerus. Insertion: Extensor expansions of digits 2–5. Action: Extends fingers at MCP and IP joints; assists wrist extension.

Extensor Digiti Minimi

Origin: Lateral epicondyle of humerus. Insertion: Extensor expansion of digit 5. Action: Extends little finger; assists wrist extension.

Extensor Indicis

Origin: Distal posterior ulna and interosseous membrane. Insertion: Extensor expansion of index finger. Action: Extends index finger; assists wrist extension.

Abductor Pollicis Longus

Origin: Posterior radius, ulna and interosseous membrane. Insertion: Base of 1st metacarpal. Action: Thumb abduction and extension at carpometacarpal joint.

Extensor Pollicis Brevis

Origin: Posterior radius and interosseous membrane. Insertion: Base of proximal phalanx of thumb. Action: Extends thumb at MCP and CMC joints.

Extensor Pollicis Longus

Origin: Posterior ulna and interosseous membrane. Insertion: Base of distal phalanx of thumb. Action: Extends thumb, especially at interphalangeal joint.