Brachioradialis muscle

At a glance

English

Brachioradialis muscle

Latin (TA2)

Musculus brachioradialis

System

Muscle

Region

Upper limb

Side

Paired, left and right

About the brachioradialis muscle

Brachioradialis forms the fleshy outer border of the forearm just below the elbow and can be seen standing out when the elbow is bent against resistance with the thumb pointing up. Although it lies at the front and acts as a flexor, it belongs developmentally to the back (extensor) compartment, which is why its nerve is the radial nerve rather than the musculocutaneous nerve that supplies the other elbow flexors.

The muscle arises from the humerus, along the upper two-thirds of its lateral supracondylar ridge, and from the lateral intermuscular septum of the arm. Its fusiform belly runs down the radial side of the forearm, becoming a flat tendon around the middle of the forearm, and attaches to the lateral side of the lower radius just above its styloid process. At the elbow, the muscle makes the outer border of the cubital fossa. Beneath it run the radial artery and the superficial branch of the radial nerve, and between it and brachialis lies the radial nerve itself as it enters the forearm.

Brachioradialis bends the elbow. It is most effective when the forearm is half-way between palm up and palm down, the position used when lifting a hammer or a mug, and when speed is needed or the elbow is already partly flexed. It also tends to bring the forearm back towards this mid position: from palm down it helps supination, and from palm up it helps pronation. It works with biceps and brachialis, while triceps and anconeus oppose it. It is supplied directly by the radial nerve (C5, C6) above the elbow, and its blood comes from the radial recurrent artery and the radial collateral artery.

Tapping its tendon just above the wrist produces the brachioradialis reflex, used to test the fifth and sixth cervical segments. Its tendon is also a landmark in surgery on the distal radius, and it can be detached and moved as a tendon transfer to restore lost movement after nerve injury.

Attachments, action and supply

Origin

Humerus, upper two-thirds of its lateral supracondylar ridge, and the lateral intermuscular septum.

Insertion

Lateral surface of the distal radius, just proximal to the styloid process.

Action

Flexes the elbow, most strongly with the forearm in mid-pronation; returns the forearm towards the mid position from full pronation or supination.

Nerve supply

Radial nerve (C5, C6).

Blood supply

Radial recurrent artery and the radial collateral branch of the profunda brachii artery.