Learning Objectives
After studying this section, you should be able to:
- Describe the layers and organization of the anterior forearm muscles
- Identify the attachments, actions, and innervation of each muscle
- Understand the neurovascular supply of the anterior compartment
- Recognize key clinical and anatomical relationships
The anterior compartment of the forearm contains muscles primarily responsible for flexion of the wrist and digits and pronation of the forearm.
These muscles are arranged into three layers based on depth:
| Layer | Muscles |
|---|---|
| Superficial | Flexor carpi ulnaris, Palmaris longus, Flexor carpi radialis, Pronator teres |
| Intermediate | Flexor digitorum superficialis |
| Deep | Flexor digitorum profundus, Flexor pollicis longus, Pronator quadratus |
Innervation
- Median nerve: Most muscles
- Ulnar nerve:
- Flexor carpi ulnaris
- Medial half of flexor digitorum profundus
Blood Supply
- Ulnar artery
- Radial artery
In this section, we examine the anatomy, attachments, actions, innervation, and clinical relevance of the muscles in the anterior compartment of the forearm.
Superficial Layer
All superficial muscles share a common flexor origin from the medial epicondyle of the humerus.
Flexor Carpi Ulnaris
Attachments
- Humeral head: medial epicondyle
- Ulnar head: olecranon
- Inserts on: pisiform, hook of hamate, base of 5th metacarpal
Actions: Wrist flexion and adduction
Innervation: Ulnar nerve
Palmaris Longus
(Absent in ~15% of people)
Attachments
- Origin: medial epicondyle
- Insertion: flexor retinaculum and palmar aponeurosis
Actions: Weak wrist flexion
Innervation: Median nerve
Flexor Carpi Radialis
Attachments
-
Origin: medial epicondyle
-
Insertion: base of 2nd and 3rd metacarpals
Actions: Wrist flexion and abduction
Innervation: Median nerve
Pronator Teres
The lateral border forms the medial boundary of the cubital fossa.
Attachments
- Origin: medial epicondyle and coronoid process of the ulna
- Insertion: lateral mid-shaft of radius
Actions: Forearm pronation
Innervation: Median nerve
Intermediate Layer
Flexor Digitorum Superficialis
This muscle lies between the superficial and deep layers and serves as a key anatomical landmark. The median nerve and ulnar artery pass between its two heads.
Attachments
- Origin: medial epicondyle and radius
- Splits into four tendons that pass through the carpal tunnel
- Inserts on the middle phalanges of digits 2–5
Actions
- Flexes MCP and PIP joints
- Assists wrist flexion
Innervation: Median nerve
Deep Layer
Flexor Digitorum Profundus
Attachments
- Origin: ulna and interosseous membrane
- Inserts on the distal phalanges of digits 2–5
Actions
- The only muscle that flexes the DIP joints
- Also flexes the MCP joints and wrist
Innervation
- Medial half (ring & little fingers): ulnar nerve
- Lateral half (index & middle): median nerve (AIN)
Flexor Pollicis Longus
Attachments
- Origin: anterior radius and interosseous membrane
- Insertion: distal phalanx of thumb
Actions
- Flexes thumb IP and MCP joints
Innervation:
- Median nerve (anterior interosseous branch)
Pronator Quadratus
A square-shaped muscle deep in the distal forearm.
Attachments
- Origin: anterior ulna
- Insertion: anterior radius
Actions:
- Forearm pronation
Innervation:
- Median nerve (anterior interosseous branch)
