Extensor carpi radialis brevis

The ECRB starts at the bony prominence on the outside of the elbow (the lateral epicondyle of the humerus). From there, it runs down the outer forearm, crosses the wrist, and attaches to the base of the metacarpal bone leading to the middle finger (the third metacarpal). Breaking down its name, “brevis” means short, “radialis” refers to the direction of the radius on the thumb side of the forearm, “carpi” refers to the wrist, and “extensor” means a muscle that straightens or extends.

Its job is to bend the wrist backward, toward the back of the hand. Working with the Extensor carpi radialis longus, which runs alongside it, it also helps tilt the wrist slightly toward the thumb. These two muscles and the other extensor muscles all belong to the Wrist extensors. A branch of the Radial nerve controls this muscle.

At its origin, the ECRB attaches to the elbow bone together with other extensor muscles through a shared tendon (the common extensor tendon), so the forces involved in using the wrist or fingers converge at this one point.

Rather than producing large, noticeable movements, the ECRB works quietly when you grip something. When the muscles that bend your fingers grip an object, they also create a force that tends to bend the wrist. The extensors contract at the same time to keep the wrist straight. They work during activities such as:

• Holding a mouse for long periods while working at a computer
• Lifting a frying pan or pot while cooking
• Wringing out a cleaning cloth or twisting a jar lid
• Swinging a racket or club in tennis, badminton, or golf
• Picking up a baby or carrying a heavy shopping bag

Repeating these movements over long periods can leave the outside of the elbow feeling stiff or achy. Many people describe a sharp, electric pain on the outside of the elbow when lifting a cup or shaking hands.

Tennis elbow (lateral epicondylopathy) refers to pain around the area where tendons attach on the outside of the elbow. Many publications describe the origin of the ECRB as the part most closely associated with this condition among the various tendons, so the ECRB is often singled out in discussions of tennis elbow. Despite the name, people who do not play racket sports can experience it too, and it can develop through hand-intensive work or household tasks. It is often introduced alongside Medial epicondylitis, or golfer’s elbow, which occurs in a similar location on the inside of the elbow.

• Try spreading out your gripping effort. Rather than gripping tightly with just your fingertips, support the object with your whole palm to help reduce the load concentrated on the extensors.
• Try keeping your wrist straight. When using a mouse or keyboard, adjust your wrist support or the height so your wrist does not bend to one side.
• Avoid continuing the same movement for too long. About once an hour, shake out your wrists or gently circle them.
• Stretch gently. Extend your arm forward with the back of your hand facing up, then use your other hand to gently press your wrist downward. Hold for 15–30 seconds at a point where you feel a comfortable stretch along the outer forearm. If it hurts, reduce the intensity.
• Build strength gradually. With a light dumbbell, slowly bend your wrist backward, then lower it even more slowly, 2–3 times a week. Gradually increase the repetitions and weight within a pain-free range.
• Check your equipment. You can review your racket’s grip thickness, the weight of your tools, and the use of elbow supports alongside the information on a Counterforce brace.

Consult a professional if the outside of your elbow keeps hurting even with rest, pain wakes you at night, or your hand feels weak and you keep dropping things. Joints and nerves are also present around the outside of the elbow, so identifying which structure is causing the discomfort can help.