Dance Anatomy & Kinesiology

The Upper Extremity 423

Individual Muscles of the Radioulnar Joints

Selected Muscles of the Radioulnar Joints

The two muscles that are the most important pronators of the forearm are the pronator teres and pro-

nator quadratus. Two muscles that are particularly important supinators of the forearm are the biceps

brachii and the supinator. The biceps brachii has already been described within the context of elbow

flexion, and a description of the other muscles follows.

Attachments and Primary Actions of Pronator Teres and Pronator Quadratus

Muscle Proximal attachment(s) Distal attachment(s) Primary action(s)

Pronator teres

(PRO-na-tor TE-reez)

Medial epicondyle of

humerus

Coronoid process of ulna

Lateral aspect of middle

third of radius

Radioulnar pronation

(Assists with elbow flexion)

Pronator quadratus

(PRO-na-tor kwod-RA-tus)

Anterior aspect of lower

quarter of ulna

Anterior aspect of lower

quarter of radius

Radioulnar pronation

Pronator Teres

The pronator teres (pronation, turning palm posteriorly, or down + teres, round) is a small muscle

located anteriorly in the area of the elbow, partly covered by the brachioradialis (figure 7.43, p. 418).

It runs laterally and obliquely from its proximal attachments on the medial epicondyle of the humerus

and upper anterior ulna to its distal attachment on the lateral middle portion of the radius. As its name

suggests, the primary action of this muscle is pronation of the forearm, which it accomplishes by pulling

the radius over in front of the ulna. It can also assist with elbow flexion against resistance (Hamilton

and Luttgens, 2002).

Palpation: Sit with the fingers of the left hand placed on the anterior portion of the forearm, just

lateral to the distal biceps brachii tendon and just below the crease of the right elbow while the elbow

is flexed and the forearm is resting on your right thigh. You can feel the pronator teres contracting under

your fingers when the forearm is pronated.

Pronator Quadratus

The pronator quadratus (pronation, turning palm posteriorly, or down + quad, square, four-sided) is

located distally on the front of the forearm slightly proximal to the wrist (figure 7.43, p. 418). It is a thin,

square-shaped muscle that runs transversely between the ulna and radius, deeply right next to these

bones. As its name indicates, its action is to pronate the forearm, which it accomplishes by pulling the

lower end of the radius over and across the ulna. Electromyographic studies suggest that the pronator

quadratus is the major muscle responsible for pronation, with the pronator teres assisting, particularly

when the pronation is resisted or rapid (Hall, 1999; Hamilton and Luttgens, 2002).

Palpation: Due to its deep location, the pronator quadratus is difficult to palpate.

Attachments and Primary Actions of Supinator

Muscle Proximal attachment(s) Distal attachment(s) Primary action(s)

Supinator

(soo-pi-NA-tor)

Lateral epicondyle of humerus

Lateral aspect of upper ulna

Anterolateral aspect of upper

radius

Radioulnar supination

Supinator

The supinator (supination, turning palm anteriorly or upward) is a small, triangular-shaped muscle located

deeply and posteriorly (figure 7.44, p. 419). It runs inferiorly and laterally from its proximal attachment

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