Overview
what it is and why it mattersThumb 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 secondYour provider does the grind test — pressing the thumb into the joint and rotating it — which reproduces the pain and sometimes a grinding feel. Stress 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).
Treatment Path
how care progresses at OSI1
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.
2
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.
3
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 at OSI
if non-operative care isn't enoughSurgery 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.
Providers Who Treat Thumb CMC Osteoarthritis
sports-medicine team
Further Reading
authoritative sourcesExternal patient-education references and related OSI pages for additional background: