Brachioradialis is a large muscle that spans the lateral forearm. The muscle belly is superficial and broad near its origin on the lateral supracondylar ridge of the humerus, then tapers to form a strong tendon before inserting on the radial styloid process. The hand and wrist flexors, located on the anterior forearm, and extensors, located on the posterior forearm, are separated by the brachioradialis. Since the brachioradialis is typically large and superficial, it serves as a useful, orienting muscular landmark.

Functionally, brachioradialis works with the biceps brachii and brachialis to flex the elbow. Unlike the other two muscles, the brachioradialis originates rather than inserts near the humeroulnar joint. This arrangement, along with its broad attachment to the humerus, makes the brachioradialis very strong at the elbow joint. It is an essential prime mover for lifting and carrying heavy loads, like buckets, grocery bags, suitcases, and wheelbarrows.

The brachioradialis is strongest when the forearm is in a neutral position. This “thumbs-up” position aligns the muscle origin on the lateral edge of the humerus with the insertion on the radial styloid process near the wrist. Because it is so strong, when these landmarks are aligned, the brachioradialis will assist with pronation or supination in an effort to return the forearm to neutral. Here, it works synergistically with the pronator teres and pronator quadratus, or biceps brachii and supinator, to rotate the forearm. Repetitive use in these motions, as is common with gardeners, hair stylists, mechanics, and plumbers, may result in inflammation and pain in any of these muscles, including the brachioradialis.

The position of the forearm (pronated, supinated, or neutral) determines which muscle is the prime mover when carrying bags or doing arm curls at the gym. When lifting with a supinated forearm (palm up), the biceps brachii works the hardest and is stabilized by the wrist and hand flexors. Lifting and carrying with a pronated forearm (palm down) requires the brachialis to work the hardest and is stabilized by the wrist and hand extensors. If the forearm is neutral (thumb up), the brachioradialis is doing most of the work. This neutral position is typically the strongest and best when carrying heavy loads.

Palpating Brachioradialis

Positioning: client supine with arm resting at side and forearm neutral.

1. Locate the lateral edge of the distal humerus with your fingertips.

2. Palpate the muscle belly just distal to the lateral epicondyle.

3. Resist as your client performs elbow flexion to differentiate between the common extensor tendon and the brachioradialis.

4. Pincer grasp the muscle belly and follow distally toward the insertion on the radial styloid process.

Christy Cael is a licensed massage therapist, certified athletic trainer, and certified strength and conditioning specialist. Her private practice focuses on injury treatment, biomechanical analysis, craniosacral therapy, and massage for clients with neurological issues. She is the author of Functional Anatomy: Kinesiology and Palpation for Manual Therapists (Lippincott Williams & Wilkins, 2009). Contact her at functionalbook@hotmail.com.

Brachioradialis

Attachments

• Origin: Lateral supracondylar ridge of the humerus

• Insertion: Radial styloid process

Actions

•
Flexes elbow

• Pronates forearm from supinated to neutral

• Supinates forearm from pronated to neutral

Innervation

• Radial nerve

• C5–T1

Client Homework—Elbow Extension Stretch

1. Grasp an object you can lift with some effort and hold it at your side with a slightly bent elbow.

2. Gently straighten your elbow as you relax the arm muscles.

3. Maintain upright posture and a straight line between your shoulder, elbow, and wrist.

4. Breathe deeply as you focus on stretching the elbow and forearm.

5. Keep your wrist straight and avoid hyperextending your elbow.

6. Repeat on the other side.

Editor’s Note: The Client Homework element in Functional Anatomy is intended as a take-home resource for clients experiencing issues with the profiled muscle. The stretches identified in Functional Anatomy should not be performed within massage sessions or progressed by massage therapists, in order to comply with state laws and maintain scope of practice.