Supinator

Origin

The supinator muscle originates from the:

- lateral epicondyle of humerus;

- supinator crest and supinator fossa of ulna;

- radial collateral ligament of elbow joint;

- annular ligament of radius;

- aponeurosis that surrounds the muscle.

Insertion

The fibers of the supinator muscle travel inferiorly and 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.

Key Features & Anatomical Relations

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 that consists of superficial and deep layers. From its origin, the muscle belly travels inferolaterally over the elbow joint, spirals over the superior one third of the radius, and travels inferomedially to its insertion site.

The supinator muscle is located:

- Anterior to the anconeus, extensor carpi ulnaris, extensor digiti minimi, extensor digitorum and extensor digiti minimi muscles;

- Posterior to the brachioradialis muscle;

- Medial to the extensor carpi radialis longus and brevis muscles;

- Lateral to the radius and pronator teres muscle.

The supinator muscle contributes to the formation of the floor of the cubital fossa. In order to enter the posterior compartment of the forearm, the posterior antebrachial interosseous nerve exits the cubital fossa by traveling between the two layers of the supinator muscle.

Actions & Testing

The supinator muscle supinates the forearm at the radioulnar joints. It can be tested by pronating the forearm at the radioulnar joints against resistance while the elbow joint is held in the extended position. This position of the elbow joint prevents the biceps brachii muscle from contracting and causing supination (Standring, 2016).

References

Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.