Thumb (basal joint) arthritis

Thumb arthritis most often affects the basal joint, also called the carpometacarpal (CMC) joint, where the thumb meets the wrist. This joint lets the thumb swivel, pinch, and grip. When the smooth cartilage covering the ends of the bones wears away, the bones rub together, causing pain, stiffness, and weakness at the base of the thumb. It is a common form of hand arthritis, especially with age.

• An ache or sharp pain where the thumb meets the wrist, brought on by pinching, grasping, or twisting motions like using a key, unscrewing a jar lid, or turning a doorknob
• Aching after prolonged use, and sometimes at night
• Weakness of grip and pinch
• Tenderness and puffiness where the thumb meets the wrist
• Over time, a bony knob or squared-off appearance at the thumb's base
• Stiffness, less motion, and difficulty opening the hand wide to grasp large objects

Most thumb arthritis is osteoarthritis, which develops gradually as cartilage wears. It can also follow an injury to the joint or occur with inflammatory arthritis such as rheumatoid arthritis.

Risk is higher with:

• Age over 50
• Female sex
• A family history of hand arthritis
• An old fracture or other injury of the thumb or wrist
• Loose or very flexible joints
• Excess body weight
• Work or activities with frequent heavy pinching and gripping

A clinician asks about your symptoms and examines the thumb for swelling, tenderness, and a bump at its base. Moving the joint while gently pressing it together (a grind test) may cause pain or a grinding feeling. X-rays show narrowing of the joint, bone spurs, and how advanced the arthritis is.

Carpal tunnel syndrome often occurs alongside thumb arthritis, so your clinician may check for it as well. The changes seen on X-rays do not always match how much pain a person has.

Non-surgical care is tried first:

• A splint or brace that supports the base of the thumb, especially at night or during heavy use
• Hand therapy for exercises, joint protection techniques, and helpful tools such as jar openers and wide-grip pens
• Ice or heat, and resting from activities that cause pain
• Anti-inflammatory medication taken by mouth or applied to the skin, when appropriate
• A corticosteroid injection into the joint, which may ease pain for a period

Surgery may be considered when pain and loss of function continue despite these measures. Several procedures are used, and no single approach is right for everyone:

• Trapeziectomy: taking out the trapezium, the small wrist bone that the thumb sits on, often together with a tendon or another method to support or cushion the thumb
• Joint fusion (arthrodesis): joining the bones so the joint no longer moves, which relieves pain but limits motion
• Joint replacement (implant arthroplasty) in selected patients

Your surgeon will discuss the options, their trade-offs, and the recovery each involves.

After surgery, the thumb is protected in a cast or splint for several weeks, followed by hand therapy to restore motion and strength. Recovery is gradual: everyday use returns over a few months, and grip and pinch strength may keep improving for up to a year.

Arthritis cannot always be prevented. Using tools with larger, padded grips, sharing loads between both hands, and avoiding prolonged tight pinching may reduce strain on the base of the thumb.