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The supinator muscle is a spiral muscle located in the posterior compartment of the forearm. It rotates the radius laterally, producing a movement known as forearm supination. This movement involves rotating the palm upwards, as when receiving a bowl of soup. The supinator muscle is assisted by the biceps brachii muscle during quick, strong, or forceful supination movements. However, the biceps brachii cannot act as a supinator when the forearm is fully extended. The supinator muscle consists of superficial and deep layers, which differ in their mode of attachment. The superficial layer arises from tendinous fibres, while the deep layer originates from muscular slips. The deep branch of the radial nerve innervates the supinator muscle, and it can be affected by a condition called supinator entrapment syndrome, which can lead to selective paralysis of the muscles it serves.
| Characteristics | Values |
|---|---|
| Location | Posterior compartment of the forearm |
| Shape | Broad, spiral, long, flat |
| Function | Supinates the forearm |
| Layers | Superficial and deep |
| Innervation | Posterior interosseous nerve (C7, C8) |
| Nerve roots | C6, C5, possible C7 involvement |
| Blood supply | Superficial layer: Radial artery; Deep layer: Ulnar artery |
| Antagonist | Pronator quadratus muscle |
| Assistance | Biceps brachii muscle |
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What You'll Learn
- The supinator muscle is located in the posterior compartment of the forearm
- It rotates the radius laterally, producing forearm supination
- The supinator muscle consists of superficial and deep layers
- The muscle is innervated by the posterior interosseous nerve
- Supination strength decreases by 64% if the supinator is disabled
The supinator muscle is located in the posterior compartment of the forearm
The supinator muscle is innervated by the posterior interosseous nerve, which is a branch of the radial nerve. The radial nerve divides into deep and sensory superficial branches just proximal to the supinator muscle. This arrangement can lead to entrapment and compression of the deep part, potentially resulting in selective paralysis of the muscles served by this nerve.
The supinator muscle is one of the muscles of the deep part of the posterior compartment of the forearm. It is a long, flat fusiform type of skeletal muscle. From its origin, the muscle belly travels inferolaterally over the elbow joint, spirals over the superior one-third of the radius, and then travels inferomedially to its insertion site. The fibres of the supinator muscle insert onto the anterior, lateral, and posterior aspects of the proximal one-third of the radius, which is located superior to the insertion site of the pronator teres muscle.
The supinator muscle is the prime supinator of the forearm. It rotates the radius laterally, producing a movement known as forearm supination. This action puts the radius parallel to the ulna, bringing the hand into the supine position, with the palm facing upwards. The supinator muscle works together with the biceps brachii muscle to produce a quick, strong, and forceful supination movement or when the movement happens against resistance.
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It rotates the radius laterally, producing forearm supination
The supinator muscle is a spiral muscle located in the posterior compartment of the forearm. It is a broad muscle that curves around the upper third of the radius, connecting it with the ulna. This unique anatomy enables the supinator muscle to rotate the radius laterally, resulting in forearm supination.
Forearm supination refers to the movement of rotating the forearm so that the palm faces upward or anteriorly, similar to the position of holding a bowl of soup. During this movement, the supinator muscle rotates the radius laterally at the proximal radioulnar joint. This action brings the radius parallel to the ulna, resulting in the supination of the forearm.
The supinator muscle consists of two layers of fibres or planes, namely the superficial layer and the deep layer. These layers differ in their origin and insertion sites. The superficial layer arises from tendinous fibres, while the deep layer originates from muscular fibres. The fibres of the supinator muscle insert onto the anterior, lateral, and posterior aspects of the proximal one-third of the radius.
The supinator muscle is the prime mover during slow and unopposed supination movements. However, during quick, forceful, or resisted supination, the supinator muscle is assisted by the biceps brachii muscle. The biceps brachii cannot act as a supinator when the forearm is fully extended, so the most effective supination occurs when the elbow joint is flexed.
The supinator muscle is innervated by the posterior interosseous nerve, which is a branch of the radial nerve. The radial nerve divides into deep and sensory superficial branches just proximal to the supinator muscle. This arrangement can lead to supinator entrapment syndrome, causing potential paralysis of the muscles served by the deep radial nerve.
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The supinator muscle consists of superficial and deep layers
The supinator muscle is a spiral muscle contained in the posterior compartment of the forearm. It rotates the radius laterally, producing a movement known as forearm supination. Its antagonist is the pronator quadratus muscle, which rotates the radius medially, producing the opposite movement of pronation.
The supinator nerve branches off the medial and deep aspect of the posterior interosseous nerve. The radial nerve divides into deep and sensory superficial branches just proximal to the supinator muscle, which can lead to entrapment and compression of the deep part, potentially resulting in selective paralysis of the muscles served by this nerve. This nerve syndrome is known as supinator entrapment syndrome and can be caused by compression by various soft-tissue masses surrounding the nerve or stress caused by repetitive supination and pronation.
The supinator muscle is one of the muscles of the deep part of the posterior compartment of the forearm. It is a long, flat fusiform type of skeletal muscle. From its origin, the muscle belly travels inferolaterally over the elbow joint, spiralling over the superior one-third of the radius and travelling inferomedially to its insertion site. The fibres of the supinator muscle insert onto the anterior, lateral, and posterior aspects of the proximal one-third of the radius, which is located superior to the insertion site of the pronator teres muscle.
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The muscle is innervated by the posterior interosseous nerve
The supinator is a muscle in the posterior compartment of the forearm. It is a spiral muscle that rotates the radius laterally, producing a movement known as forearm supination. Its antagonist is the pronator quadratus muscle, which produces the opposite movement of pronation. The supinator muscle is innervated by the posterior interosseous nerve, a branch of the radial nerve.
The radial nerve divides into deep and superficial branches just proximal to the supinator muscle. This arrangement can lead to entrapment and compression of the deep part, potentially resulting in selective paralysis of the muscles served by this nerve, including the extensor muscles and the abductor pollicis longus. This nerve syndrome is known as supinator entrapment syndrome and can be caused by compression by various soft-tissue masses surrounding the nerve or stress caused by repetitive supination and pronation.
The deep branch of the radial nerve passes through the belly of the supinator in 70% of cases and via the arcade of Frohse in the remaining cases. The arcade of Frohse refers to the proximal aspect of the superficial head of the supinator muscle. The deep branch of the radial nerve becomes the posterior interosseous nerve upon exiting the supinator muscle. Its nerve roots are primarily from C6, with some C5 involvement and possible additional C7 innervation.
The supinator muscle consists of two layers of fibres: a superficial layer and a deep layer. These two layers originate from the supinator crest of the ulna, the lateral epicondyle of the humerus, the radial collateral ligament, and the annular radial ligament. The superficial layer of fibres has a tendinous origin and surrounds the upper part of the radius. The deeper layer of fibres encircles the neck of the radius above the radial tuberosity.
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Supination strength decreases by 64% if the supinator is disabled
In human anatomy, the supinator is a broad muscle in the posterior compartment of the forearm, which curves around the upper third of the radius. Its function is to supinate the forearm, or rotate the radius laterally, producing a movement known as forearm supination. The supinator is innervated by the posterior interosseous nerve, a branch of the radial nerve.
The supinator consists of two planes of fibres, or superficial and deep layers. The superficial layer receives blood from the radial artery, while the deep layer is supplied by the ulnar artery. The deep branch of the radial nerve passes through the belly of the supinator in 70% of cases, becoming the posterior interosseous nerve upon exiting the muscle. This arrangement can lead to entrapment and compression of the deep part of the nerve, potentially resulting in selective paralysis of the muscles served by it. This nerve syndrome is known as supinator entrapment syndrome.
The supinator always acts together with the biceps, except when the elbow joint is extended. It is the most active muscle in forearm supination during unresisted supination, while the biceps become increasingly active with heavy loading. Supination strength decreases by 64% if the supinator is disabled, for example, by injury. This is because the biceps cannot act as a supinator when the forearm is fully extended, so the most powerful supination occurs when the elbow joint is flexed to 90 degrees.
Supination strength can be improved through interventions such as friction massage, which has been shown to increase supinator muscle strength in patients with limited supination range of motion. Additionally, nonoperative treatments for distal biceps ruptures have been found to result in limited functional loss, indicating that supination strength can be maintained or improved without surgical intervention in some cases.
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Frequently asked questions
The supinator is a broad muscle in the posterior compartment of the forearm. It curves around the upper third of the radius and consists of two layers of fibres.
The supinator muscle supinates the forearm. This means it rotates the radius laterally, producing a movement known as forearm supination. This action puts the radius parallel to the ulna, bringing the hand into the supine position (facing anteriorly, palm up, like when holding a bowl of soup).
The supinator always acts together with the biceps brachii, except when the elbow joint is extended. The biceps brachii cannot act as a supinator when the forearm is fully extended, so the most powerful supination occurs when the elbow joint is flexed to 90 degrees.
The radial nerve divides into deep and superficial branches just proximal to the supinator muscle. This arrangement can lead to entrapment and compression of the deep part, potentially resulting in selective paralysis of the muscles served by this nerve. Supinator entrapment syndrome has many possible causes, including compression by various soft-tissue masses surrounding the nerve and stress caused by repetitive supination and pronation.
