If turning a key, opening a jar, or pinching a zipper sends a sharp ache into the base of your thumb, you are not alone. Arthritis at the base of the thumb — known as CMC (carpometacarpal) or basal joint arthritis — is one of the most common reasons adults in Boise and across the Treasure Valley seek out a hand and wrist specialist. It can develop quietly over years, then flare up when a repetitive task or an awkward grip pushes the joint past its limit.

Why the Thumb Base Wears Out

The CMC joint sits where the thumb metacarpal meets a small wrist bone called the trapezium. It is a saddle-shaped joint that allows the thumb to swivel, pinch, and oppose the fingers — motions we use hundreds of times a day. That mobility comes at a cost: the joint relies heavily on surrounding ligaments for stability, and when those ligaments loosen with age or repetitive stress, the cartilage begins to wear.

Women are affected more often than men, and symptoms typically appear after age 40. A history of thumb sprains, hands-on trade work, needlework, gardening, or long hours of phone and tablet use can all accelerate the process.

Signs It May Be More Than a Sore Thumb

Basal joint arthritis often builds slowly, and many people write off the early symptoms as fatigue or overuse. Consider an evaluation if you notice:

  • Pain at the base of the thumb with pinching, gripping, or twisting
  • Aching after activities like knitting, texting, or using hand tools
  • A visible bump or squared-off appearance at the thumb base
  • Weakness when opening jars, turning doorknobs, or writing
  • Grinding or a catching sensation when moving the thumb
  • Pain that lingers after rest or wakes you at night

How the Diagnosis Is Made

Evaluation starts with a focused history and a hands-on exam. A specialist can often reproduce the pain with a specific maneuver called the grind test, which loads the CMC joint. X-rays confirm the diagnosis and show how much cartilage remains, whether the joint has shifted, and if neighboring joints are involved. Because thumb pain can also stem from de Quervain’s tendonitis, a scaphoid problem, or referred pain from the wrist, a careful exam matters — treating the wrong structure rarely helps.

Non-Surgical Treatment Options

Most people with thumb base arthritis can be managed without surgery, especially when the condition is caught before the joint collapses. A treatment plan is typically layered, starting with the least invasive steps.

Activity modification and bracing. A well-fitted thumb spica splint rests the joint during flares and can be used at night or during aggravating tasks. Simple tool changes — larger-diameter pens, jar openers, ergonomic garden shears — reduce daily strain.

Targeted exercises. Strengthening the muscles that support the thumb, particularly the first dorsal interosseous and thenar muscles, can offload the arthritic joint. A specialist can guide which exercises are appropriate for your stage of disease.

Anti-inflammatory strategies. Topical or oral anti-inflammatories, used judiciously, can quiet flares. Corticosteroid injections into the CMC joint often provide months of relief and can be repeated when appropriate.

Surgical referral when needed. If pain persists despite conservative care and imaging shows advanced joint changes, referral for a surgical opinion is coordinated so you can weigh your options with complete information.

When to Get Evaluated

Thumb pain that changes how you use your hand deserves attention. Early evaluation gives you the widest range of non-surgical choices and helps prevent the compensations — sore wrists, tight forearms, weakened grip — that develop when one joint quietly fails. If pinching and gripping have become a daily struggle, a focused upper extremity evaluation in Boise can clarify what is happening and what to do next.