Thumb Basal Joint (CMC) Arthritis

What it is

The basal joint (carpometacarpal or CMC joint) is where the thumb meets the wrist. In thumb arthritis, the smooth cartilage lining this joint wears away. It is the second most common site of arthritis in the hand.

What causes it

Thumb arthritis is usually age-related wear, typically beginning after age 40. It is more common in women and tends to run in families. A previous thumb injury or inflammatory arthritis, such as rheumatoid arthritis or lupus, can also damage the joint.

Symptoms

• Pain at the base of the thumb with pinching, grasping, or gripping, such as opening jars or turning keys
• Swelling or stiffness at the base of the thumb
• Weakness and loss of motion as arthritis progresses
• Later, bone spurs that make the base of the thumb look enlarged

Diagnosis

An examination, including gently moving the joint to check for grinding, and X-rays confirm the diagnosis.

Treatment

Arthritis seen on X-ray generally worsens slowly over time, but symptoms do not always follow, and many people improve with simple measures.

Without surgery: a thumb brace, heat or ice, anti-inflammatory medication, hand therapy and exercises, adaptive tools and changes to how you do aggravating tasks, and corticosteroid injections.

Surgery: when pain persists despite these measures, surgery can remove part or all of the trapezium bone and cushion or suspend the thumb, using one of several techniques. Fusing the joint is another option in some patients.

Recovery

After surgery, the thumb is protected in a splint or cast, followed by hand therapy. Full recovery can take anywhere from about eight weeks to a year.