| Supinator muscle | |
|---|---|
 Posterior view of the supinator. (Right arm.) | |
| Details | |
| Origin | Lateral epicondyle ofhumerus,supinator crest ofulna,radial collateral ligament,annular ligament |
| Insertion | Lateral proximalradial shaft |
| Artery | Radial recurrent artery |
| Nerve | Deep branch of the radial nerve |
| Actions | Supinatesforearm |
| Antagonist | Pronator teres,pronator quadratus |
| Identifiers | |
| Latin | musculus supinator |
| TA98 | A04.6.02.048 |
| TA2 | 2512 |
| FMA | 38512 |
| Anatomical terms of muscle | |
In human anatomy, thesupinator is a broad muscle in theposterior compartment of the forearm, curved around the upper third of theradius. Its function is tosupinate the forearm.[1]
The supinator consists of two planes of fibers, between which passes thedeep branch of the radial nerve. The two planes arise in common—the superficial one originating as tendons and the deeper by muscular fibers[2]—from thesupinator crest of theulna, thelateral epicondyle of thehumerus, theradial collateral ligament, and theannular radial ligament.[1]
The superficial fibers (pars superficialis) surround the upper part of the radius, and are inserted into the lateral edge of theradial tuberosity[3] and the oblique line of the radius, as low down as the insertion of thepronator teres. The upper fibers (pars profunda) of the deeper plane form a sling-likefasciculus, which encircles the neck of the radius above the tuberosity and is attached to the back part of its medial surface; the greater part of this portion of the muscle is inserted into the dorsal and lateral surfaces of the body of the radius, midway between the oblique line and the head of the bone.[2]
The proximal aspect of the superficial head is known as thearcade of Frohse or the supinator arch.
It is innervated by the deep branch of theradial nerve. The deep branch then becomes theposterior interosseous nerve upon exiting the supinator muscle. Its nerve roots are primarily from C6, with some C5 involvement. There is also possible additional C7 innervation.
The radial nerve divides into deep and sensory superficial branches just proximal to the supinator muscle—an arrangement that can lead to entrapment and compression of the deep part, potentially resulting in selectiveparalysis of the muscles served by this nerve (the extensor muscles and theabductor pollicis longus.)[4] Many possible causes are known for this nerve syndrome, known as supinator entrapment syndrome, including compression by various soft-tissued masses surrounding the nerve, and stress caused by repetitive supination and pronation.[5]
The deep radial nerve passes through the belly of supinator in 70% of cases and via thearcade of Frohse in remaining cases.[6]
Encircling the radius, supinator brings the hand into the supinated position. In contrast to thebiceps brachii, it is able to do this in all positions of elbow flexion and extension.[1]
Supinator always acts together with biceps, except when the elbow joint is extended.[7] It is the most active muscle in forearm supination during unresisted supination, while biceps becomes increasingly active with heavy loading.[8] Supination strength decreases by 64% if supinator is disabled by, for example, injury.[9]
The term "supinator" can also refer more generally to a muscle that causes supination of a part of the body. In older texts, the term "supinator longus" was used to refer to thebrachioradialis, and "supinator brevis" was used to describe the muscle now known as the supinator.
.jpg)
.jpg)
This article incorporates text in thepublic domain frompage 454 of the 20th edition ofGray's Anatomy(1918)
