Brachioradialis · What Is It, Location, and More

The brachioradialis is a superficial muscle located on the posterior compartment of the forearm that forms the lateral border of the cubital fossa, a triangular depression at the anterior aspect of the elbow between the upper arm and forearm.   

Innervation of the brachioradialis muscle is produced by the radial nerve (C5-C6), which runs adjacent to the muscle. Similarly, blood supply comes from the radial recurrent artery, a branch of the radial artery. 

Even though the brachioradialis is anatomically grouped in as an extensor muscle of the posterior compartment due to its location, functionally it acts as a weak flexor of the elbow. Specifically, it functions to stabilize the elbow joint in conjunction with the biceps and brachialis muscle when flexing the forearm, especially when the forearm is in a mid-pronated (neutral) position. Pronation describes the position when one’s palm is placed downward, while supination occurs when the palm is faced upward. Mid-pronation occurs when the hand is between full pronation and full supination, so the thumb is pointing upwards and the palm is facing inward (e.g., holding a glass of water or shaking someone’s hand). Additionally, the brachioradialis assists in returning the forearm to a neutral position when it is fully pronated or supinated, however, it cannot rotate the forearm beyond neutral. 

The brachioradialis muscle can become injured due to trauma or overuse. Conditions that affect the brachioradialis include muscle strain, tendonitis, avulsion fracture, or weakness with cervical radiculopathy. Brachioradialis strain can be caused by sudden trauma to the arm muscle, while tendonitis may be due to repetitive movement. An avulsion fracture occurs when the brachioradialis tendon forcefully pulls away from its attachment site, causing a fragment of bone to tear off along with the tendon. Finally, nerve root entrapment in the cervical spine may cause cervical radiculopathy, which can affect the innervation of the brachioradialis muscle and result in arm weakness during elbow flexion. This clinical finding can be further assessed using the brachioradialis reflex, a deep tendon reflex that evaluates the integrity of the C5 and C6 nerve roots via the radial nerve.   

To elicit the brachioradialis reflex, the examiner strikes the brachioradialis tendon approximately 2-3 cm above the radial styloid process while the individual’s forearm is relaxed. A normal response is a slight elbow flexion or wrist movement. An absent or diminished reflex may indicate cervical radiculopathy involving the C5 or C6 nerve roots.