Thumb CMC Arthritis

Overview

what it is and why it matters

Thumb CMC arthritis, also called basal joint arthritis, is wear-and-tear arthritis at the very base of your thumb, where the thumb's long bone meets a small wrist bone called the trapezium. It's the second most common kind of arthritis in the hand. The shape of that joint is unusual, like two saddles facing each other, which is what gives your thumb its remarkable range of motion. The trade-off is that the joint takes a lot of stress every time you pinch or grip, and over time the cartilage in it wears down.

It's far more common in women (about 10 to 1) and usually shows up after age 40. The classic symptoms: a deep aching pain at the base of the thumb that flares when you pinch or open a jar, swelling on the thumb side of the wrist, and sometimes a visible bump where the thumb bone has shifted out of its original position.

Diagnosis

exam first, imaging second

Diagnosis starts with a focused physical exam of the thumb. X-rays of the thumb base show the classic arthritis changes: narrowed joint space, dense bone, and bone spurs at the edges of the joint. The X-rays also tell us whether the next joint up the wrist is also involved (which changes the surgical plan).

Zoomed PA X-ray of the thumb CMC joint showing joint space narrowing and sclerosis between the first metacarpal base and the trapezium. — **X-rays of advanced thumb-base arthritis.** Two views of the same thumb. The cushioning cartilage at the base of the thumb has worn away, the bones now sit close together, and the joint has begun to shift out of line, which is what makes the base of the thumb look and feel prominent. Patient imaging de-identified per HIPAA (45 CFR §164.514)

Zoomed oblique X-ray of the thumb CMC joint showing dorsal subluxation of the first metacarpal on the trapezium and peripheral osteophytes. — **X-rays of advanced thumb-base arthritis.** Two views of the same thumb. The cushioning cartilage at the base of the thumb has worn away, the bones now sit close together, and the joint has begun to shift out of line, which is what makes the base of the thumb look and feel prominent. Patient imaging de-identified per HIPAA (45 CFR §164.514)

Treatment Path

how care progresses

Thumb spica splinting

A thumb splint that holds the thumb still while letting your fingers work normally takes the load off the arthritic joint and is often the single most effective non-surgical step. Off-the-shelf and custom-molded versions both work.

Activity modification

Small everyday changes help a lot: jar openers, fatter pen grips, electric can openers, anything that takes pinch loading off the joint during the activities you do most.

Occupational / hand therapy

Hand therapy strengthens the small muscles at the base of the thumb that help stabilize and offload the arthritic joint, and teaches you positions and movements that don't aggravate it.

Corticosteroid injection
An ultrasound-guided steroid injection placed precisely into the small CMC joint reduces inflammation. How long the relief lasts varies: some patients get months, others a few weeks.

Surgical Options

if non-operative care isn't enough

Surgery is the answer when months of bracing, therapy, and injection haven't quieted the pain in a moderate-to-severely arthritic thumb base. The procedure (a thumb CMC arthroplasty) reconstructs the joint, typically removing the worn-out trapezium bone and using a nearby tendon to suspend the thumb in good position.

Thumb CMC arthroplasty

Reconstruction of the arthritic basal thumb joint.

Learn about this procedure →

Providers Who Treat Thumb CMC Arthritis

sports-medicine team

Michael S. Vrana, M.D.

David B. Templin, M.D.

Trent Twitero, M.D.

Frequently Asked

questions we hear in clinic

What is thumb CMC arthritis?

It is wear-and-tear arthritis at the very base of the thumb, where the thumb's long bone meets a small wrist bone called the trapezium. It is also called basal joint arthritis, and it is the second most common kind of arthritis in the hand.

Why does the base of the thumb wear out?

The shape of that joint is unusual, like two saddles facing each other, which is what gives your thumb its remarkable range of motion. The trade-off is that the joint takes a lot of stress every time you pinch or grip, and over time the cartilage in it wears down.

Who tends to get it?

It is far more common in women, about 10 to 1, and usually shows up after age 40.

What does it feel like?

The classic symptoms: a deep aching pain at the base of the thumb that flares when you pinch or open a jar, swelling on the thumb side of the wrist, and sometimes a visible bump where the thumb bone has shifted out of its original position.

How is it diagnosed?

With an exam of the thumb base and X-rays. Stress X-rays show the classic arthritis changes, narrowed joint space, dense bone, and bone spurs at the edges of the joint. They also tell us whether the next joint up the wrist is involved, which changes the surgical plan.

What helps before surgery comes up?

A thumb spica splint that holds the thumb still while letting your fingers work normally takes the load off the arthritic joint, and it is often the single most effective non-surgical step. Small everyday changes help too: jar openers, fatter pen grips, electric can openers, anything that takes pinch loading off the joint. Hand therapy strengthens the small muscles at the base of the thumb that help stabilize and offload the joint, and an ultrasound-guided steroid injection placed precisely into the small CMC joint reduces inflammation.

How long does a steroid injection last?

It varies. Some patients get months of relief, others a few weeks.

When is surgery the answer, and what does it involve?

Surgery is the answer when months of bracing, therapy, and injection have not quieted the pain in a moderate-to-severely arthritic thumb base. The procedure, a thumb CMC arthroplasty, reconstructs the joint, typically removing the worn-out trapezium bone and using a nearby tendon to suspend the thumb in good position.