Logan Steele
The supinator muscle is a broad muscle located in the posterior compartment of the forearm, curving around the upper third of the radius. Its main function is to supinate the forearm, rotating it laterally and putting the hand in a supine position. The supinator consists of two layers of fibres, or planes, with the deep branch of the radial nerve passing between them. The muscle works together with the biceps to produce powerful supination, except when the elbow is fully extended.
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What You'll Learn
- The supinator muscle is a spiral muscle located in the posterior compartment of the forearm
- Its function is to supinate the forearm, rotating the radius laterally
- The supinator consists of two layers of fibres, superficial and deep, which differ in their mode of attachment
- The supinator muscle is innervated by the deep branch of the radial nerve, which becomes the posterior interosseous nerve
- Supinator entrapment syndrome is a nerve syndrome that can be caused by compression of the deep branch of the radial nerve
The supinator muscle is a spiral muscle located in the posterior compartment of the forearm
The two layers of the supinator muscle differ in their mode of attachment. The superficial layer arises from tendons, surrounding the upper part of the radius, while the deep layer originates with already formed muscular slips. These layers receive blood supply from different sources, with the superficial layer receiving blood from the radial artery and the deep layer supplied by the ulnar artery.
The supinator muscle works together with the biceps brachii to produce powerful supination, except when the elbow is fully extended. In contrast, the antagonist muscle to the supinator is the pronator quadratus, which produces the opposite movement of pronation.
The supinator muscle is innervated by the deep branch of the radial nerve, which becomes the posterior interosseous nerve upon exiting the muscle. This arrangement can be susceptible to supinator entrapment syndrome, where compression or entrapment of the deep branch of the nerve may lead to selective paralysis of the muscles it serves.
The supinator muscle, along with the brachialis, forms the floor of the cubital fossa. It originates from the ulna and humerus, inserting onto the posterior surface of the radius. This anatomy enables the supinator muscle to rotate the radius laterally, bringing the hand into a supine position.
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Its function is to supinate the forearm, rotating the radius laterally
The supinator muscle is a broadly-shaped muscle located in the posterior compartment of the forearm. It is a supinator of the forearm, and its main function is to supinate the forearm, rotating the radius laterally. This movement involves the supinator muscle rotating the radius laterally at the proximal radioulnar joint, bringing the radius parallel to the ulna. This action brings the hand into the supine position, with the palm facing up, as when holding a bowl of soup.
The supinator muscle is innervated by the deep branch of the radial nerve, which becomes the posterior interosseous nerve upon exiting the muscle. This nerve passes between the muscle's two layers or heads, which originate from the ulna and humerus. The two layers of the supinator muscle differ in their mode of attachment. The superficial layer arises from tendinous fibres, while the deep layer originates from already formed muscular slips.
The supinator muscle works together with the biceps brachii muscle to produce a quick, strong, and forceful supination movement or when the movement occurs against resistance. However, the biceps brachii cannot assist in supination when the elbow is fully extended. Therefore, the most powerful supination occurs when the elbow joint is flexed at a 90-degree angle, such as when turning a screwdriver or uncorking a bottle.
The supinator muscle is essential for forearm supination, and its strength is significantly reduced if the supinator is disabled or injured. Its role in rotating the radius laterally and bringing the hand into the supine position is crucial for various everyday movements and tasks that require forearm supination.
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The supinator consists of two layers of fibres, superficial and deep, which differ in their mode of attachment
The supinator is a muscle in the posterior compartment of the forearm. It is a supinator of the forearm, meaning 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 a supine position, palm up, like when holding a bowl of soup.
The supinator muscle consists of two layers of fibres, or two planes of fibres, that originate in common from the supinator crest of the ulna, the lateral epicondyle of the humerus, the radial collateral ligament, and the annular radial ligament. The two layers of fibres are the superficial layer and the deep layer. The superficial layer has a tendinous origin and surrounds the upper part of the radius. The deep layer originates with already formed muscular slips.
The supinator muscle is innervated by the deep branch of the radial nerve, which becomes the posterior interosseous nerve upon exiting the supinator muscle. The nerve roots are primarily from C6, with some C5 involvement, and there is also possible additional C7 innervation. 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 branch, potentially resulting in selective paralysis of the muscles served by this nerve.
The supinator muscle is the prime supinator of the forearm, but it often works with the biceps brachii for powerful supination. However, the biceps brachii is unable to supinate when the elbow is extended. The supinator is always active during forearm supination, but its role decreases as the load increases, with the biceps becoming increasingly active.
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The supinator muscle is innervated by the deep branch of the radial nerve, which becomes the posterior interosseous nerve
The supinator is a muscle in the posterior compartment of the forearm. It is a supinator of the forearm, rotating the radius laterally to produce a movement known as forearm supination. This action puts the radius parallel to the ulna, bringing the hand into a supine position.
The supinator muscle has a broad origin from the ulna and humerus, with two layers of fibres. The superficial layer of fibres has a tendinous origin, surrounding the upper part of the radius. The deep layer originates with already formed muscular slips. The supinator muscle is innervated by the deep 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 branch, potentially resulting in selective paralysis of the muscles served by this nerve. This nerve syndrome is known as supinator entrapment syndrome.
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 posterior interosseous nerve passes between the muscle's superficial and deep heads to enter the extensor compartment of the forearm.
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Supinator entrapment syndrome is a nerve syndrome that can be caused by compression of the deep branch of the radial nerve
The supinator is a broad muscle in the posterior compartment of the forearm, curving around the upper third of the radius. Its function is to supinate the forearm. The supinator consists of two layers of fibres, between which lies the deep branch of the radial nerve. The supinator muscle has a broad origin from the ulna and humerus.
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 branch, potentially resulting in selective paralysis of the muscles served by this nerve. This nerve syndrome is known as supinator entrapment syndrome.
Supinator entrapment syndrome can be caused by compression of the deep branch of the radial nerve, which becomes the posterior interosseous nerve upon exiting the supinator muscle. The nerve roots are primarily from C6, with some C5 involvement. There may also be additional C7 innervation. The deep radial nerve passes through the belly of the supinator in 70% of cases and via the arcade of Frohse in the remaining cases.
Many possible causes are known for supinator entrapment syndrome, including compression by various soft-tissue masses surrounding the nerve, and stress caused by repetitive supination and pronation. Supination strength decreases by 64% if the supinator is disabled by injury, for example. The supinator muscle is assisted by the biceps brachii muscle for quick, strong, and forceful supination movements, or when the movement happens against resistance. However, the biceps brachii cannot act as a supinator when the forearm is fully extended.
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Frequently asked questions
The supinator muscle is a broad muscle located 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 can be done with the elbow in any position of flexion or extension. However, the bicep brachii muscle assists the supinator muscle in quick, strong, or forceful supination movements.
The supinator muscle rotates the radius laterally at the proximal radioulnar joint. This action puts the radius parallel to the ulna, bringing the hand into the supine position (facing anteriorly, palm up, like holding a bowl of soup).
