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The extensor digitorum muscle, also known as the extensor digitorum communis (EDC) muscle, is a muscle of the superficial layer of the posterior compartment of the forearm. It is a long muscle that extends the wrist and elbow and separates the fingers as it extends them. The extensor digitorum is innervated by the posterior interosseous nerve, a branch of the radial nerve. It is one of the extrinsic muscles of the hand and can be easily palpated in the lateral aspect of the posterior forearm, especially during the extension of the hand.
| Characteristics | Values |
|---|---|
| Muscle name | Extensor digitorum muscle (ED) or Extensor digitorum communis (EDC) |
| Type of muscle | Long, broad, fusiform type of skeletal muscle |
| Location | Superficial layer of the posterior compartment of the forearm |
| Innervation | Posterior interosseous nerve, a branch of the radial nerve |
| Origin | Common extensor tendon attached to the lateral epicondyle of the humerus |
| Insertion | Divides into four tendons that insert into the middle and distal phalanges of the fingers |
| Function | Extends the phalanges, wrist, and elbow; separates the fingers as it extends them |
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What You'll Learn
Extensor digitorum communis (EDC) muscle
The extensor digitorum communis (EDC) muscle, also known as the extensor digitorum muscle, is a muscle of the posterior forearm found in humans and other animals. It is a superficial muscle, located in the posterior compartment of the forearm. It is the most superficial muscle of the posterior forearm.
The extensor digitorum arises from the lateral epicondyle of the humerus, by the common tendon, and from the intermuscular septa between it and the adjacent muscles, as well as the antebrachial fascia. It is one of the extrinsic muscles of the hand. The extensor digitorum is innervated by the posterior interosseous nerve, which is a continuation of the deep branch of the radial nerve (C7 and C8).
The extensor digitorum extends the phalanges, the wrist, and the elbow. It also separates the fingers as it extends them. In the fingers, the extensor digitorum acts on the proximal phalanges, extending the metacarpophalangeal joint. The extension of the proximal and distal interphalangeal joints is primarily mediated by the dorsal and palmar interossei, as well as the lumbricals of the hand. The extensor digitorum is responsible for extending the fingers, and its isolated contraction causes hyperextension of the MCP joints.
The tendons of the extensor digitorum pass through the 4th extensor compartment at the wrist. The tendon divides into four tendons in the distal forearm, which then pass through a separate compartment of the dorsal carpal ligament within a mucous sheath. These tendons diverge on the back of the hand and are inserted into the middle and distal phalanges of the fingers. The tendons are connected by oblique intertendinous connections, which vary among individuals.
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Location and anatomy
The extensor digitorum muscle (also known as the extensor digitorum communis or ED muscle) is a muscle of the posterior forearm in humans and other animals. It is a long, broad, fusiform type of skeletal muscle. It is located in the posterior compartment of the forearm, originating from a common tendon attached to the lateral epicondyle of the humerus. This tendon serves as a proximal attachment for the extensor digiti minimi, extensor carpi radialis brevis, and extensor carpi ulnaris muscles.
The extensor digitorum is one of the extrinsic muscles of the hand and is involved in extending the wrist and elbow. It also extends the phalanges of the hand, acting principally on the proximal phalanges to extend the metacarpophalangeal joint. The extension of the proximal and distal interphalangeal joints is mediated predominantly by the dorsal and palmar interossei and lumbricals of the hand.
The extensor digitorum divides into four tendons in the distal forearm, which pass through a separate compartment of the dorsal carpal ligament within a mucous sheath. These tendons then diverge on the back of the hand and are inserted into the middle and distal phalanges of the fingers. The tendons attach to their respective digits via extensor expansion, covering the dorsal surfaces of digits 2-5.
The extensor digitorum is innervated by the posterior interosseous nerve, a branch of the radial nerve. It is situated medial to the extensor carpi radialis brevis muscle and lateral to the extensor digiti minimi and extensor carpi ulnaris muscles.
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Innervation
The extensor digitorum communis (EDC) muscle is located in the forearm and is responsible for extending the wrist joint and the medial four digits (the second, third, fourth, and fifth fingers) at the metacarpophalangeal joints and, secondarily, at the interphalangeal joints.
The radial nerve divides off the posterior cord of the brachial plexus and, as it travels to the elbow, it innervates the triceps muscle. A motor nerve that branches off the radial nerve is the posterior interosseous nerve (PIN), also known as the dorsal branch of the radial nerve. The PIN innervates the EDC muscle, along with the extensor digitorum medialis (EDM) and extensor carpi ulnaris (ECU) muscles, from the superficial wrist extensor compartment.
The PIN branches off the radial nerve at the level of the radiocapitellar joint and is typically located immediately proximal to the supinator muscle in an area of a fibrous band known as the arcade of Frohse. After innervating the EDC, EDM, and ECU muscles, the PIN then innervates the abductor pollicis longus (APL), extensor pollicis brevis (EPB), extensor pollicis longus (EPL), and extensor indicis proprius (EIP) muscles.
The EDC muscle is supplied by the posterior interosseous artery and the radial recurrent artery. It has been found to play a role in the pathology of lateral epicondylitis due to its role in extending the middle finger, which can reproduce pain on resisted extension.
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Function
The extensor digitorum muscle (also known as extensor digitorum communis or ED) is a muscle of the superficial layer of the posterior compartment of the forearm. It is one of the extrinsic muscles of the hand.
The extensor digitorum muscle is involved in multiple functions. Firstly, it extends the distal phalanges at the distal interphalangeal joints of the index, middle, ring, and little fingers. This means that it helps to straighten the fingers, particularly at the outermost joints closest to the fingernails.
Secondly, the muscle extends the middle phalanges at the proximal interphalangeal joints of the same fingers. This action occurs at the middle joints of the fingers, helping to further straighten them.
Thirdly, the extensor digitorum muscle extends the proximal phalanges at the metacarpophalangeal joints of the same fingers. This action occurs at the innermost finger joints, closest to the palm, contributing to the full extension of the fingers.
Additionally, this muscle assists in the extension of the hand at the radiocarpal (wrist) joint. This means that it plays a role in straightening the wrist and extending the hand.
The muscle can be easily palpated, or felt, during the extension of the hand when it is contracted. To test the muscle, one can try extending the fingers against resistance while the forearm is held in a pronated position, or palm-down orientation. This action will cause the muscle to become visible and palpable.
The extensor digitorum muscle is innervated by the posterior interosseous nerve, which is a branch of the radial nerve. This nerve helps to control the muscle's functions and movements.
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Testing
The extensor digitorum muscle, also known as the extensor digitorum communis (EDC) muscle, is a muscle of the posterior forearm. It is a long muscle that generates a pull to extend the four medial fingers and their metacarpophalangeal and interphalangeal joints.
To test the extensor digitorum muscle, one can try extending the fingers against resistance while the forearm is held in the pronated position. This test was suggested by Standring in 2016. During this test, the muscle can be seen and palpated. The extensor digitorum muscle can be easily palpated in the lateral aspect of the posterior forearm, especially during the extension of the hand when the muscle is contracted.
Another way to test the muscle is to observe its origin, insertion, and innervation. The extensor digitorum muscle originates from the lateral epicondyle of the humerus, by the common tendon, and from the intermuscular septa between it and the adjacent muscles. It is innervated by the posterior interosseous nerve, which is a branch of the radial nerve. The muscle inserts into the middle and distal phalanges of the fingers. Opposite the metacarpophalangeal articulation, each tendon is bound by fasciculi to the collateral ligaments and serves as the dorsal ligament of this joint.
The extensor digitorum muscle can also be observed through its function. It extends the phalanges, the wrist, and the elbow. It tends to separate the fingers as it extends them. In the fingers, the extensor digitorum acts principally on the proximal phalanges, extending the metacarpophalangeal joint.
Additionally, the muscle's relationship with other structures can be examined. For example, the extensor digitorum muscle is situated medial to the extensor carpi radialis brevis muscle and lateral to the extensor digiti minimi and extensor carpi ulnaris muscles. Its tendons are placed deep to the extensor retinaculum, between the tendons of the extensor digiti minimi and extensor pollicis longus.
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Frequently asked questions
EDC stands for Extensor Digitorum Communis. It is a muscle of the posterior forearm in humans and other animals.
The EDC muscle is located in the posterior compartment of the forearm. It is one of the extrinsic muscles of the hand.
The EDC muscle extends the phalanges, the wrist, and the elbow. It also separates the fingers as it extends them.
The EDC muscle can be tested by extending the fingers against resistance while the forearm is held in the pronated position.
