Supinator Muscle Anatomy

The supinator lies deep in the cubital fossa and, along with the brachialis, forms its floor. Spiraling medially and distally from its continuous, osseofibrous origin, this sheet-like muscle envelops the neck and proximal part of the shaft of the radius.

Supinator Muscle Anatomy

The wide supinator muscle consists of superficial and deep layers. These layers differ in the type of origin, the superficial layer arises by tendinous fibers, while the deep layer originates with already formed muscular slips.

See Also: Forearm Muscles Anatomy & Function

Both of these layers originate from the: lateral epicondyle of humerus, radial collateral ligament of humeroulnar joint, annular ligament of the superior radioulnar joint, supinator crest of ulna and the adjacent part of ulnar fossa.

It inserts onto the lateral, posterior and anterior surfaces of proximal 1/3 of radius

The deep branch of the radial nerve passes between its muscle fibers, separating them into superficial and deep parts, as it passes from the cubital fossa to the posterior part of the arm. As it exits the muscle and joins the posterior interosseous artery, it may be referred to as the posterior interosseous nerve.

The blood supply to the supinator muscle is based on its layers, the superficial layer receives blood supply from the radial artery, via its radial recurrent branch, while the deep layer is supplied by the ulnar artery, through its posterior interosseous and posterior interosseous recurrent arteries.

The supinator is the prime mover for slow, unopposed supination, especially when the forearm is extended. The biceps brachii also supinates the forearm and is the prime mover during rapid and forceful supination against resistance when the forearm is flexed (e.g., when a right-handed person drives a screw).

The radial nerve divides into deep and sensory superficial branches proximal to the supinator muscle, which can cause entrapment and compression of the deep branch. This may lead to selective paralysis of the muscles innervated by it. Various factors can contribute to this condition, known as supinator entrapment syndrome, including compression from soft tissue masses near the nerve, and stress from repetitive supination and pronation movements.

References & More

1. Cael, C. (2010). Functional anatomy: Musculoskeletal anatomy, kinesiology, and palpation for manual therapists. Philadelphia, PA: Wolters Kluwer Health/Lippincott, Williams & Wilkins.
2. Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2014). Clinically Oriented Anatomy (7th ed.). Philadelphia, PA: Lippincott Williams & Wilkins.
3. Clinically Oriented Anatomy – 8th Edition
4. Glover NM, Black AC, Murphy PB. Anatomy, Shoulder and Upper Limb, Radial Nerve. [Updated 2023 Nov 5]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: Pubmed