We have a total of 8 muscles at  front of the forearm and 12 muscles at back of forearm.

Muscle of front of Forearm

Deep Muscle

There are three muscles in the deep group. These are pronator quadratus , Flexor digitorum profundus ,Flexor pollicis longus .

Pronator quadratus

Origin: Anterior surface of ulna

Insertion: Anterior surface of radius

Action: Pronator of the forearm.

Flexor digitorum Profundus

origin: Anterior surface of ulna

Insertion: Base of the distal phalanges (2-5 fingers)

Action :

• • Flexor of 2 – 5 fingers at the metacarpophalangeal and interphalangeal joint
  • Accessory flexion longus

Flexor pollicis longus

Origin: Anterior surface of Radius

Insertion: Base of distal phalanges of the thumb

Action :

• • Flexion of thumb at MCP and IP Joint
  • Accessory Flexion of hand

Superficial muscle

There are five muscles in the superficial group. These are pronator teres, flexor carpi radialis, palmaris longus , flexor carpi ulnaris and flexor digitorum superficialis .

Pronator there

Origin: Medial epicondyle of humerus

Insertion: Anterolateral surface of radius

Flexor Carpi Radialis

Origin: Medial epicondyle of humerus

Insertion: Base of 2nd and 3rd metacarpals

Palmaris longus

Origin: Medial epicondyle of humerus

Insertion : Palmar Aponeurosis

Flexor Carpis Ulnaris

Origin: Medial epicondyle of humerus

Insertion: Hamatum, Pisiform, and base of 5th Metacarpal.

Flexor digitorum superficial

origin: medial epicondyle of humerus

Insertion: Each tendon is divided into 2 slips which are inserted on the sides of the middle phalanx of the 2nd to 5th digits

Muscles of the back of the forearm

Superficial muscle

There are seven superficial muscles on back of the forearm:

Anconeus

Origin: Lateral epicondyle of humerus

Insertion: Lateral surface of the olecranon process of ulna

Action: Extended elbow joint

Brachioradialis

Origin: Upper 2/3rd of the lateral supracondylar ridge of humerus.

Insertion: Base of the styloid process of the radius

Action: Flexes forearm at elbow joint; rotate forearm to mid-prone position from supine or prone positions.

Extensor carpi radialis longus

Origin: Lower 1/3rd of lateral supracondylar ridge of humerus

Insertion: posterior surface of base of the second metacarpal bone

Action: Extend and abducts hand at the wrist joint.

Extensor carpi radialis brevis

Origin: Lateral epicondyle of humerus

Insertion: Posterior surfaces of the base of the third metacarpal

Action: Extend and abducts hand at the wrist joint.

Extensor digitorum

Origin: Lateral epicondyle of humerus

Insertion: bases of middle phalanges of the 2nd – 5th digits

Action: Extends finger of the hand

Extensor digit minimi

Origin: Lateral epicondyle of humerus

Insertion: Extensor expansion of little finger

Action: Extendmetacarpophalangeal joint of the little finger

extensor carpi ulnaris

Origin: Lateral epicondyle of humerus

Insertion: Base of the fifth metacarpal bone

Action: Extend and adduct the hand at wrist joint.

Deep Muscle

These are as follows ;

Supinator

Origin: Lateral epicondyle of humerus, annular ligament of superior radioulnar joint, supinator crest of ulnar, and depression anterior to it.

Insertion: Neck and whole shaft of upper one-third of radius

Action: Supination of the forearm when elbow is extended

Extensor pollicis bervis

Origin: Posterior surface of shaft of radius

Insertion: Base of proximal phalanx of thumb

Action: Extends metacarpophalangeal joint of the thumb

Extensor pollicis longus

Origin: Posterior surface of shaft of ulna

Insertion: Base of distal phalanx of thumb

Action: Extends distal phalanx of thumb

Abductor pollicis longus

Origin: Posterior surface of shaft of radius and ulna

Insertion: Base of the first metacarpal bone.

Action: Abducts and extends thumb

Extensor indicis

Origin: Posterior surface of shaft of ulna

Insertion: Extensor expansion of index finger

Action: Extends metacarpal; phalangeal joint of the index finger.