Forearm Muscles: The forearm is the region of the upper limb between the elbow and the wrist. The forearm muscles divided into-
- Anterior compartment
- Posterior compartment
Anterior Compartment
Anterior compartment of the forearm muscles divided into superficial & deep muscles.
Superficial muscles:
- Pronator teres
- Palmaris longus
- Flexor carpi radialis
- Flexor carpi ulnaris
- Flexor digitorum superficialis
Pronator teres: It has two head.
- Origin:
- Humeral head: medial epicondyle of humerus
- Ulnar head: Medial border of coronoid process of ulna
- Insertion:
- Middle of the lateral aspect of the shaft of the radius.
- Action:
- Pronation of forearm
Flexor carpi ulnaris:
- Origin: It has two head.
- Humeral head: Medial epicondyle of humerus
- Ulnar head: Medial aspect of olecranon process of ulna and posterior border of ulna
- Insertion:
- Pisiform bone, the hook of hamate and base of the 5th metacarpal bone
- Action:
- Flexes and abducts hand at wrist joint
Palmaris longus:
- Insertion:
- Flexor retinaculum and palmar aponeurosis
- Action:
- Flexes wrist joint
Flexor carpi radialis:
- Insertion:
- Bases of 2nd and 3rd metacarpal bones
- Action
- Flexes and abducts hand at wrist joint
Flexor digitorum superficialis
- Origin:
- All superficial muscles are arises from the medial epicondyle of humerus but they are inserted into the different part except
- Insertion:
- The middle phalanx of 2nd to 5th digits ( four fingers)
- Action:
- Flexes middle phalanx of fingers and assists in flexing proximal phalanx and wrist joint
- Nerve supply:
- All muscles are supplied by median nerve except flexor carpi ulnaris supplied by the ulnar nerve
Deep muscles:
- Flexor digitorum profundus
- Flexor pollicis longus
- Pronator quadratus
Flexor digitorum profundus( hybrid muscle):
- Origin:
- Upper three-fourths of the anterior and medial surface of the shaft of ulna
- Upper three-fourths of the posterior border of ulna
- Medial surface of the olecranon and coronoid processes of the ulna
- Insertion:
- Flexor retinaculum( medial 4 digits)
- Nerve supply:
- Medial half by the ulnar nerve
- Lateral half by anterior interosseous nerve(c8 , t1)
- Action:
- Flexor of distal phalanges after the flexor digitorum superficialis has flexed the middle phalanges.
Flexor pollicis longus:
- Origin:
- Upper three- fourths of the anterior surface of the shaft of the radius
- Insertion:
- Palmar surface of the distal phalanx of the thumb
- Nerve supply:
- Anterior interosseous nerve
- Action:
- Flexes the distal phalanx of the thumb
Pronator quadratus:
- Origin:
- The oblique ridge on the lower one-fourth of the anterior surface of the shaft of ulna
- Insertion:
- Lower one-fourth of the anterior surface and the anterior border of the radius, Ulnar notch
- Nerve supply:
- Anterior interosseous nerve
- Action:
- Pronate the forearm
Posterior Compartment
Posterior compartment of the forearm muscles divided into superficial & deep muscles.
Superficial muscles:
- Anconeus
- Brachioradialis
- Extensor carpi radialis longus
- Extensor carpi radialis brevis
- Extensor digitorum
- Extensor digiti minimi
- Extensor carpi ulnaris
Superficial muscles:
- Origin:
- All are arises from the lateral epicondyle of the humerus.
Anconeus:
- Insertion:
- The lateral surface of olecranon process of ulna
- Nerve supply:
- Radial nerve
- Action:
- Extends elbow joint
Brachioradialis:
- Insertion:
- The base of styloid process of radius
- Nerve supply:
- Radial nerve
- Action:
- Flexes forearm at the elbow joint and rotates forearm to the midprone position from supine or prone positions
Extensor carpi radialis longus:
- Insertion:
- The posterior surface of the base of the 2nd metacarpal bone
- Nerve supply:
- Radial nerve
- Action:
- Extends and abducts hand at wrist joint
- Extends and abducts hand at wrist joint
Extensor carpi radialis brevis:
- Insertion:
- The posterior surface of the base of the third metacarpal bone
- Nerve supply:
- Deep branch of the radial nerve
- Action:
- Extends and abducts hand at wrist joint
Extensor digitorum:
- Insertion:
- Bases of middle phalanges of the 2nd-5th digits
- Nerve supply:
- Deep branch of the radial nerve
- Action:
- Extends fingers of the hand
Extensor digiti minimi:
- Insertion:
- Extensor expansion of little finger
- Nerve supply:
- Deep branch of the radial nerve
- Action:
- Extends metacarpophalangeal joint of the little finger
Extensor carpi ulnaris:
- Insertion:
- The base of the fifth metacarpal bone
- Nerve supply:
- Deep branch of the radial nerve
- Action:
- Extends and adducts hand at wrist joint
Deep muscles:
- Supinator
- Abductor pollicis longus
- Abductor pollicis brevis
- Extensor pollicis longus
- Extensor indicis
Supinator:
- Origin:
- Lateral epicondyle of humerus
- Insertion:
- Neck and shaft of upper 1/3rd of radius
- Nerve supply:
- Deep branch of the radial nerve
- Action:
- Supination of the forearm when the elbow is extended
Abductor pollicis longus:
- Origin:
- The posterior surface of the shaft of radius and ulna
- Insertion:
- The base of the first metacarpal bone
- Nerve supply:
- Deep branch of the radial nerve
- Action:
- Abducts and extends the thumb
Extensor pollicis brevis:
- Origin:
- The posterior surface of the shaft radius
- Insertion:
- The base of proximal phalanx of the thumb
- Nerve supply:
- Deep branch of the radial nerve
- Action:
- Extends metacarpophalangeal joint of the thumb
Extensor pollicis brevis:
- Origin:
- The posterior surface of the shaft of ulna
- Insertion:
- The base of distal phalanx of the thumb
- Nerve supply:
- Deep branch of the radial nerve
- Action:
- Extends distal phalanx of the thumb
Common Elbow Conditions: Tennis Elbow, Golfers Elbow & Cubital Tunnel Syndrome.
Forearm Movements
Supination of forearm muscles-Supinator.
Pronation of forearm muscles-Pronator teres & Pronator quadratus.
Elbow flexor muscles-Biceps brachii, Brachialis, Brachioradialis, Pronator teres.
Elbow extensor muscles-Triceps brachii & Anconeus