If you have thumb pain or arthritis at the base of your thumb, you may wonder if something in your body is making it worse. Scientists looked at a muscle called the abductor pollicis longus to see if how it attaches in your hand might be connected to thumb arthritis. They studied 104 hands from people who had passed away.
Here are three important things they found:
- Almost everyone has more than one place where this thumb muscle attaches.
- Nearly all of the hands studied already had thumb arthritis.
- The way the muscle attaches does not seem to cause or worsen arthritis.
Key Findings at a Glance
- Research shows that 95% of people have multiple attachment points for the abductor pollicis longus muscle
- According to this study, 97% of dissected hands showed signs of thumb arthritis at the base joint
- Studies indicate that 71% of arthritis starts in the outer part of the thumb joint
- Medical evidence found no link between how the muscle attaches and how bad the arthritis is
- 42% of hands had an extra tendon going to the muscle area at the base of the thumb
What Is the Abductor Pollicis Longus Muscle?
Let us start with the basics. The abductor pollicis longus is a muscle in your forearm. It helps you move your thumb away from your hand. You use it every time you spread your thumb out to hold something big like a cup or a ball.
This muscle has a tendon that travels down to your thumb. The tendon attaches to bones in your thumb and hand. But the exact place where it attaches can be different from person to person.
What Did the Study Find?
Scientists in France looked at 104 hands. They wanted to see two things. First, they wanted to know where the tendon attaches. Second, they wanted to see if arthritis showed up in these hands.
Here is where it gets interesting.
The researchers wanted to know if the way the tendon attaches might cause arthritis. Or make it worse. This kind of arthritis is called rhizarthrosis. It happens at the base of your thumb where your thumb meets your wrist.
Where Does This Muscle Attach?
According to this study, most people have more than one attachment point. In fact, 95% of the hands studied had multiple places where the tendon attached.
Let us look closer at what the scientists found:
| Attachment Location | How Often |
|---|---|
| Base of the first thumb bone | Always present in all hands |
| Trapezium bone in the wrist | 70% of hands |
| Thenar eminence muscles | 42% of hands |
The first attachment point is always there. Every hand studied had the tendon attached to the base of the first thumb bone. This bone is called the first metacarpal.
But many hands also had extra attachments. Seven out of ten hands had an attachment to a small wrist bone called the trapezium. This bone sits right under your thumb.
You may be wondering what the thenar eminence is.
Research shows that 42% of hands had an extra tendon slip going to this area. That means almost half of people have this extra connection. The scientists said this was surprisingly common.
What About the Arthritis?
Now we come to the arthritis part. This is what many people with thumb pain care about most.
According to this study, 97% of the hands showed signs of rhizarthrosis. That means almost every hand studied had some arthritis in the thumb joint. This number seems very high. But remember, these were older people who had passed away. Thumb arthritis becomes more common as people get older.
Where Does Arthritis Start in the Thumb Joint?
The scientists noticed something important. The arthritis did not affect the whole joint evenly. It seemed to start in one spot more often than others.
Studies indicate that 71% of the time, the outer part of the joint showed arthritis first. This is called the lateral compartment. The joint surface on the outside edge of your thumb got damaged before other parts.
The researchers believe this outer area is probably where the problem begins. Then it spreads to other parts of the joint over time.
Does the Muscle Connection Cause Arthritis?
This is the big question the scientists wanted to answer. If the way your tendon attaches makes arthritis worse, then maybe doctors could do something early to prevent it.
Some doctors had wondered if cutting certain tendons early might stop arthritis from happening. This procedure is called tenotomy.
But according to this study, the answer is no. Medical evidence found no connection between how the tendon attaches and how severe the arthritis is. People with different attachment patterns had arthritis just as often. And the arthritis was just as bad no matter how many attachment points they had.
This means cutting tendons early would probably not help prevent thumb arthritis. The scientists said they cannot recommend this based on what they found.
Your Questions Answered
Does everyone have the same thumb muscle attachments?
No. Research shows that 95% of people have multiple attachment points, but where exactly the muscle attaches varies from person to person. Some people have extra connections that others do not have.
Can the way my thumb muscle attaches cause my arthritis?
According to this study, no clear link was found between muscle attachment patterns and arthritis severity. Almost everyone studied had arthritis regardless of how their muscle attached. The attachment pattern does not seem to cause or worsen the problem.
Where does thumb arthritis usually start?
Studies indicate that thumb arthritis most often starts on the outer edge of the joint. This area is called the lateral compartment. According to medical evidence, 71% of cases showed arthritis beginning in this spot first.
Should I have surgery on my thumb tendon to prevent arthritis?
Based on this research, cutting thumb tendons early to prevent arthritis is not recommended. The scientists found no evidence that this would help. Always talk with your doctor about what is right for your specific situation.
What This Means for You
If you have thumb pain or have been told you have rhizarthrosis, this study offers some comfort. Your anatomy is probably normal. Having extra tendon attachments does not mean you are more likely to get arthritis or have worse arthritis.
The study also shows that thumb arthritis is very common as people age. You are not alone. Understanding where the arthritis tends to start may help your doctor plan the best treatment for you.
The good news is that preventive tendon surgery does not seem necessary. This means you can focus on treatments that actually help with your symptoms right now.
Talk with your doctor about your options. There are many ways to manage thumb arthritis and reduce your pain.
About This Site
We simplify medical science so you can understand what research says about thumb pain and rhizarthrosis. Every article we share comes from real published scientific studies. We read the complex medical language and explain it in words anyone can understand. You are not alone in your journey with thumb pain. We invite you to explore more articles on this site to learn about your condition and your options.
Important Note
This article shares information from medical research. It is not medical advice. It cannot replace talking with your doctor. Every person is different. Your doctor knows your health history and can give you advice that fits your needs. If you have thumb pain or questions about arthritis, please see a healthcare professional.
Scientific Source
This article is based on research by Bouchlis, G., Bhatia, A., Asfazadourian, H., Touam, C., Vacher, C., and Oberlin, C., published in Annales de Chirurgie de la Main et du Membre Supérieur in 1997.
https://doi.org/10.1016/s0753-9053(97)80047-6
Now that you understand the anatomy, learn how rhizarthrosis is diagnosed and what the Eaton stages mean.
Diagnosis Guide
