Why does thumb arthritis cause pain & deformity?

Thumb pain can make simple daily tasks like gripping a cup or buttoning a shirt surprisingly hard. If you’ve noticed swelling, unusual bending of your thumb joints, or difficulty moving your thumb, you might be wondering what’s happening. This article explains what scientists uncovered about thumb arthritis, also called rhizarthrosis, and how it affects your muscles.

Here’s what you’ll learn:

• What happens to your joints with thumb arthritis?
• How your thumb muscles change with arthritis.
• Why thumb deformities occur and what the study discovered.

In this article:

• What is Rhizarthrosis?
• What Happens to Your Thumb in Arthritis?
• How Do Your Thumb Muscles Change & Cause Deformity
• Frequently Asked Questions
• Final Thoughts
• Disclaimer

What is Rhizarthrosis?

Rhizarthrosis is another name for thumb arthritis, especially at the base of the thumb where it connects to the wrist. This joint is called the carpometacarpal joint. It can wear down over time, which means the cartilage, the cushion between bones, breaks apart. Without that cushion, the bones rub against each other and you feel pain.

You might notice swelling, stiffness, or changes in how your thumb looks. Some people lose their grip strength, and their thumb may start bending in unusual ways.

What Happens to Your Thumb in Arthritis?

The study mentioned advanced thumb arthritis does specific things to your thumb:

• The base of your thumb joint can move out of place, causing “subluxation,” which is a partial dislocation.
• Your thumb may twist inward toward your palm. Doctors call this an adduction deformity.
• The joint near your thumbnail can bend backwards into what’s called hyperextension, where it moves beyond the normal range.

All of these changes make using your thumb much harder.

How Do Your Thumb Muscles Change & Cause Deformity

Let’s look closer at what the study found. It looked at the muscles in your thumb with arthritis:

• The M. abductor pollicis brevis, or a muscle that lifts your thumb away from the palm, works differently because the direction it pulls in actually changes. Imagine pulling on a door handle in a strange direction, it does not work the same.
• The flexor pollicis brevis, a muscle that helps you bend your thumb, becomes smaller, about 50% smaller, according to the study.
• Electromyography (a test that checks how muscles work by measuring their electrical activity) showed that some thumb muscles lose their ability to fire correctly. They don’t contract the way they’re supposed to, which makes your thumb weaker.

Here is where it gets interesting. These problems in your muscles create an imbalance. Think of it like a system of ropes where one rope pulls too tightly while others loosen. Without balance, your thumb can become stuck in a “Z-deformity.” This means your thumb bends in odd ways and is harder to straighten.

Frequently Asked Questions

What should I do next?

Your thumb plays a huge role in daily life, so understanding how arthritis affects it can help you take healthy next steps. If these symptoms sound familiar, don’t hesitate to visit your doctor or physical therapist. Strengthening exercises and treatments, like supportive splints, might be a helpful option.

At this site, we make medical science simple and easy to understand, especially for those facing thumb pain and rhizarthrosis. Every article is based on trusted published research. Be sure to browse our other blogs to find more information you can put into action!

Is this medical advice?

This article is for educational purposes only. It is not intended to be medical advice. For any health concerns, please consult a qualified healthcare professional.

Study Source

Schoneberger, M.; Koebke, J. (1989). Rhizarthrosis and thenar muscles. A clinico-anatomic study.