Thumb-Base Arthritis: Diagnosis & Treatment

Osteoarthritis of the thumb-base joint, the first carpometacarpal (CMC) joint, is a very common cause of pain when you pinch, grip, open jars, turn keys or do up buttons. It's particularly common in women from middle age onwards. The reassuring part is that most people improve without surgery: the best-supported starting point is active, multimodal treatment, sensible changes to painful activities, hand exercises and a supportive splint, with an injection considered if symptoms stay troublesome. Surgery is reserved for persistent, function-limiting pain that hasn't improved with good non-operative care.

What is thumb-base arthritis?

The thumb-base joint, the first carpometacarpal (CMC) joint, sits where the thumb metacarpal meets a small wrist bone called the trapezium. It's a saddle-shaped joint that gives the thumb its wide range of movement for pinching and gripping, which also makes it prone to wear over time. In osteoarthritis the cartilage thins, the joint can become less stable, and bony changes develop, causing pain, weakness and sometimes a prominent bump at the base of the thumb. It's especially common in women from midlife onwards.

As with arthritis elsewhere, the X-ray appearance doesn't always match how much pain someone has, so treatment is guided by your symptoms and function, not the scan alone.

Making sure the pain is from the thumb-base joint

The first step is confirming the pain really is coming from the CMC joint, because other thumb-side wrist problems, particularly De Quervain's tenosynovitis, can feel similar but need different treatment. Examination usually reproduces the pain at the joint, for example with a gentle grind or load test, and I check the joint's stability and movement. Ultrasound, and where useful an X-ray, help confirm the diagnosis and rule out the mimics.

First-line: activity changes, exercises and a splint

For most people treatment starts here, and for many this is enough.

Education and activity modification

The aim is to reduce unnecessary strain without stopping normal thumb movement, avoiding all activity just leads to stiffness and weakness. Practical adjustments include:

• reducing sustained or forceful tip-to-tip pinching;
• using larger or padded handles;
• using jar-openers and other assistive devices;
• taking breaks during repetitive gripping;
• using both hands to lift heavier objects;
• keeping the wrist relatively straight when lifting;
• sliding objects rather than lifting them where practical.

A hand therapist can pinpoint the movements that aggravate your symptoms and suggest practical alternatives for work, hobbies and daily life.

Hand exercises

Exercises can reduce pain and improve strength and function, particularly when done regularly. A 2024 systematic review found clinically meaningful short-term improvements in pain and disability compared with no treatment. A programme might include gentle thumb movement, controlled thumb opposition, isometric thumb abduction and extension, thumb-base stability work, strengthening of the thenar and first dorsal interosseous muscles, and gradual grip and pinch strengthening. Exercise should be challenging but tolerable, mild discomfort during or shortly after is acceptable, but a big increase in pain lasting into the next day usually means the resistance, repetitions or technique need adjusting.

Evidence: good short-term benefit for pain and function

Splinting

A thumb-base (CMC, or CMC-MCP) splint supports the painful joint during gripping and pinching. Recent evidence suggests a rigid splint may be particularly helpful for medium-term hand function, though no single design suits everyone. It can be worn during activities that provoke pain, at work or hobbies, at night if pain disturbs sleep, or for extra support during a flare. It should support the base of the thumb without being too tight or unnecessarily restricting the fingers, and it's used alongside exercises, not instead of them.

Evidence: helpful, particularly a rigid splint for medium-term function

Pain-relieving medication

A topical anti-inflammatory gel may be suitable when medically appropriate, and is often preferred before oral anti-inflammatory tablets because less of the drug reaches the rest of the body. Oral anti-inflammatories can help for a limited period but aren't right for everyone, particular care is needed with kidney disease, previous stomach ulcers, cardiovascular disease, anti-inflammatory-triggered asthma, or if you take anticoagulants or certain other medicines. Medication is most useful when it lets you move and rehabilitate comfortably, rather than becoming the only treatment.

Corticosteroid injection

An injection into the thumb-base joint may be considered when pain stays troublesome despite a proper trial of exercises, splinting and activity changes, or when pain is preventing rehabilitation. A corticosteroid injection can give temporary relief, but responses vary and good-quality studies haven't shown a consistent or lasting benefit for everyone, and it doesn't reverse the arthritis or repair cartilage.

Ultrasound guidance lets me see the joint and confirm the needle is in the right place, which helps when the joint is difficult to access, the anatomy is altered, or a previous landmark-guided injection didn't work. That said, better accuracy hasn't consistently translated into better pain or function than a carefully performed landmark injection. The potential risks are usually minor:

• a temporary increase in pain;
• a change in skin colour;
• thinning of the skin or underlying fat;
• infection, which is rare;
• a temporary rise in blood glucose in people with diabetes.

Repeated injections are considered case by case, because the benefit may lessen and repeated steroid can increase the risk of local tissue effects.

Evidence: variable and temporary, useful for selected patients, not a cure

PRP and hyaluronic acid

Platelet-rich plasma (PRP) and hyaluronic acid (HA) injections are sometimes offered for thumb-base arthritis. Some studies suggest PRP may give longer-lasting relief than steroid, and HA may improve function in selected patients, but the studies are generally small, use different products and schedules, and give inconsistent results, so neither is established as the best injection here. They're best regarded as optional specialist treatments rather than routine first-line care, and the cost, availability and uncertain benefit should be discussed first. I should be clear that I don't currently offer PRP at Insight MSK; hyaluronic acid for small joints is available in selected cases.

Evidence: inconsistent, optional rather than routine

When is surgery considered?

Surgery may be appropriate when pain and loss of function stay substantial despite a well-delivered programme of non-operative treatment. The decision should be based on your symptoms and their effect on daily life, not the X-ray alone, so it's considered when pain keeps interfering with work, sleep, self-care or activities that matter to you.

The most established operation is a trapeziectomy, removing the trapezium bone beneath the thumb metacarpal. Several variations exist, including ligament reconstruction, tendon interposition, joint replacement and fusion. Importantly, current evidence doesn't show that routinely adding ligament reconstruction and tendon interposition produces better results than trapeziectomy alone, a 2026 Cochrane review found these additions may give little or no extra benefit in pain or function. The right operation still depends on your age, joint pattern, occupation, expectations and the surgeon's assessment. Recovery usually takes several months, and it's worth discussing beforehand the expected improvement, the period of immobilisation, the hand therapy involved, the time to recover strength, possible complications, and the likely time away from work and valued activities.

Evidence: effective for persistent, function-limiting pain

A practical treatment pathway

Rather than jumping to any single treatment, I work through a stepwise plan:

1. Confirm the pain is coming from the thumb-base joint and assess its effect on function.
2. Begin education, activity modification and a tailored exercise programme.
3. Add a comfortable thumb-base or CMC-MCP splint.
4. Consider a topical anti-inflammatory if medically suitable.
5. Review progress and adjust the exercises, splint or activity plan.
6. Consider a corticosteroid injection if pain remains intrusive or prevents rehabilitation.
7. Use ultrasound guidance when accurate joint access is difficult or particularly important.
8. Discuss specialist injection options only after reviewing their uncertain benefits, risks and costs.
9. Seek a hand-surgery opinion if substantial pain and disability persist despite comprehensive non-operative care.

Key message

Frequently asked questions

References