Anterior Compartment of the Forearm
Anterior compartment of forearm contains flexor muscles and pronators innervated by the median nerve.
The anterior compartment of the forearm is also known as the flexor-pronator compartment. It contains muscles primarily responsible for flexion of the wrist and fingers as well as pronation of the forearm. The compartment is bordered by the antebrachial fascia and is separated from the posterior compartment by the interosseous membrane and intermuscular septa.
Boundaries
| Structure | Description |
|---|---|
| Anterior | Skin and superficial fascia |
| Posterior | Radius, ulna, interosseous membrane |
| Medial & Lateral | Intermuscular septa, medial and lateral borders of forearm |
Muscle Layers
The anterior compartment has three layers: superficial, intermediate, and deep.
Superficial Layer (5 Muscles)
| Muscle | Origin | Insertion | Innervation | Function |
|---|---|---|---|---|
| Pronator teres | Medial epicondyle & coronoid process of ulna | Lateral surface of radius | Median nerve | Forearm pronation, weak elbow flexion |
| Flexor carpi radialis | Medial epicondyle | Base of 2nd and 3rd metacarpals | Median nerve | Flexion and radial deviation of wrist |
| Palmaris longus | Medial epicondyle | Palmar aponeurosis | Median nerve | Wrist flexion; tenses palmar fascia |
| Flexor carpi ulnaris | Medial epicondyle & olecranon | Pisiform, hook of hamate, base of 5th metacarpal | Ulnar nerve | Flexion and ulnar deviation of wrist |
| Flexor digitorum superficialis (also considered intermediate) | Medial epicondyle, radius | Middle phalanges of digits 2–5 | Median nerve | Flexion at PIP joints and MCP joints |
Deep Layer (3 Muscles)
| Muscle | Origin | Insertion | Innervation | Function |
|---|---|---|---|---|
| Flexor digitorum profundus | Ulna and interosseous membrane | Distal phalanges of digits 2–5 | Medial half: ulnar nerve Lateral half: median nerve (AIN) |
Flexion at DIP joints |
| Flexor pollicis longus | Radius and interosseous membrane | Distal phalanx of thumb | Median nerve (anterior interosseous nerve) | Flexion of thumb at IP joint |
| Pronator quadratus | Distal ulna | Distal radius | Median nerve (AIN) | Forearm pronation |
Contents
- Median nerve: Supplies most muscles; travels between FDS and FDP
- Ulnar nerve: Supplies FCU and medial half of FDP; travels medially with ulnar artery
- Radial and ulnar arteries: Main blood supply to muscles
- Anterior interosseous nerve and artery: Supply deep muscles
Function
- Flexion: Of wrist, MCP, PIP, and DIP joints
- Pronation: Of the forearm by pronator teres and pronator quadratus
- Grip assistance: Through coordinated flexor action during grasping
Blood Supply
- Ulnar artery: Primary source for superficial and deep branches
- Radial artery: Contributes to lateral side
- Anterior interosseous artery: Deep muscle supply
Innervation
- Median nerve: All muscles except FCU and medial FDP
- Ulnar nerve: FCU and medial (ulnar) half of FDP
Surface Anatomy
The tendons of FDS and FCR become prominent in the distal forearm and at the wrist crease. The palmaris longus (if present) is visible during wrist flexion.
Clinical Significance
- Pronator syndrome: Compression of median nerve between heads of pronator teres
- Anterior interosseous syndrome: Isolated motor neuropathy causing inability to make the “OK” sign
- Compartment syndrome: Deep fascia limits expansion, requiring fasciotomy in severe swelling
- Tendonitis: Overuse of flexor tendons can lead to medial epicondylitis ("golfer's elbow")
Comparative Anatomy
In quadrupeds, the flexor compartment supports locomotion. In humans, it has evolved for fine control of hand and finger movement essential for precision tasks like writing, typing, and tool use.
