You may not think much about your thumb—after all, it’s a digit and not even a finger—but it plays an important role in your everyday life. You use your thumb to grasp and pinch objects, open jars, play the guitar, dress yourself, operate tools, and perform countless other tasks.

And even if you do appreciate your thumb, you might not be aware of how the first carpometacarpal or “CMC” joint helps it do its job. The CMC joint is located where the thumb (metacarpal) bone meets the wrist (carpal) bone.

As this joint becomes worn, often due to age, it can lead to a painful condition called thumb arthritis (also known as CMC arthritis or basal joint arthritis). Arthritis refers to inflammation in a joint, causing the pain, stiffness, and swelling that makes it so difficult to perform even simple tasks. Thumb arthritis is the second most common type of arthritis in the hand.

Xuan Luo, MD, a Yale Medicine hand, shoulder, and elbow surgeon, draws from evolutionary history when he explains thumb arthritis to patients. “If you look at certain ancestors of ours, not all of them had opposable thumbs [meaning they can be placed opposite the fingers, which is what allows us to grasp objects]. This is a relatively new evolutionary invention,” Dr. Luo says. “And like any new feature on your car or computer, it’s not always tested well and tends to wear out first. As we get older, that CMC joint in particular often wears out, causing pain at the base of the thumb.”

Treatment for thumb arthritis starts conservatively with the patient wearing a soft brace. If that doesn’t work, injections at the base of the palm may work. And if there still isn’t relief, surgery is an option. 

Joints are connections between two or more bones. A normal joint is made of two smooth, cartilage-covered bone surfaces that fit well together and glide when the body moves. But if the smooth surface wears out—often, just from the wear and tear that comes with age—then the bone surfaces no longer fit together and arthritis can develop.  

There are many different types of arthritis, but the kind that most often affects the thumb is osteoarthritis, the most common form of arthritis. With osteoarthritis, the cartilage inside your joints starts to break down, causing changes in the bone that typically start slowly and worsen over time.

An injury to the thumb raises the likelihood that you will develop thumb arthritis. Other conditions, including lupus and rheumatoid arthritis, might also cause deterioration of the basal joint.

Thumb arthritis typically occurs after age 40. It is more common in women, but it can affect men, too. There is a genetic predisposition that makes people more likely to develop thumb arthritis.

“Thumb arthritis is unbelievably common, and if we look at the X-rays of people in their 50s, 60s, and 70s, 30 to 50 percent of that population can have it,” Dr. Luo says. “But not everyone will have symptoms that are severe enough to require any treatment.” 

Pain in the thumb is the most common symptom of thumb arthritis. You might feel pain when you are pinching or gripping objects, Dr. Luo says. “You may also notice a little bump at the base of your thumb,” he adds, explaining that this would be a bone spur, or a projection that develops along joints as a result of inflammation, including osteoarthritis.

Other symptoms may include the following: 

• Swelling and tenderness at the base of the thumb
• An ache after prolonged use of the thumb
• Loss of strength when gripping or pinching with your thumb
• Limited motion

To make a diagnosis of thumb arthritis, your doctor will start by gathering your medical history, discussing symptoms, prior injuries, and what activities cause you pain.

For the physical examination, your doctor will hold the basal joint while rocking your thumb back and forth, Dr. Luo says. If that causes pain or a grinding sound, it means the bones are rubbing directly against each other and likely have thumb arthritis. An X-ray can confirm the diagnosis. 

The first method of treatment for thumb arthritis involves wearing a soft brace to limit the movement of your thumb, which allows the joint to rest. If the condition is more serious, a hard brace can be used, and either type can be worn overnight or intermittently throughout the day.

Other noninvasive steps include taking anti-inflammatory medications, modifying your activities, and icing the joint for 5 to 15 minutes several times a day.

If these methods do not help, the next step would be to inject a steroid medication directly into the joint. The injection may provide relief for several months and can be repeated indefinitely. Both men and women typically respond well to such conservative treatments at first, and for some, they may be all that is needed. But the treatments don’t stop arthritis from progressing.

When nonsurgical approaches are no longer effective, surgery is an option. The best type of surgery for you depends on a number of factors, including the progression of the disease and how painful the symptoms are. In most cases, surgery for thumb arthritis involves removing some or part of trapezium (a bone in the thumb joint) with varying ways of stabilizing the joint.

“We take out the arthritic bone and reconstruct the tendon or ligament to hold the thumb in place,” Dr. Luo explains. “This surgery works great, but has a long recovery. It may take up to one year for complete recovery. A lot of my patients don’t like me at their first follow-up, but as the months roll by, they really like it.” 

The physicians in Yale Medicine’s Hand & Upper Extremity Surgery Program specialize in evaluating and treating injuries and musculoskeletal disorders that affect your daily movements. We offer the latest technological advances and we are active in research that can lead to better treatments.

“At Yale Medicine, we offer the complete range of care to patients, with occupational therapists on site at multiple locations and a new state-of-the-art outpatient surgery center at Yale New Haven Hospital’s St. Raphael Campus,” Dr. Luo says.