Welcome back to another (somewhat longer) article covering the basics of a common hand surgery topic. Today I would like to discuss thumb arthritis. Specifically, the most common type of thumb arthritis known as thumb CMC joint arthritis or ‘basilar’ thumb arthritis.

Thumb CMC arthritis is extremely common. If you live long enough, you are essentially guaranteed to develop it.

There’s a lot to discuss here. Let’s dive in.

What is arthritis?

We could spend pages just discussing arthritis itself. But let’s simplify.

Remember that ‘arthritis’ is a general term. All it means is a loss of the smooth cartilage that normally pads the ends of bones whenever two bones come together. Two bones come together to form a ‘joint.’ Examples would include your hip, knee, or shoulder. The cartilage ‘padding’ will cushion the impact between the two bones during activity and movement.

Arthritis can happen anywhere in the body. As soon as the cartilage is lost, the remaining rough bone ends will rub together, often resulting in pain.

However, there are a few characteristics that distinguish thumb CMC base arthritis from arthritis in the rest of the body.

If you’d like more specifics on all types of arthritis, I go into much more detail in an article linked here.

Pain

The first differentiator inherent to thumb CMC arthritis has to do with pain. Believe it or not, there is actually a very poor correlation between the severity of CMC arthritis seen on x-ray and the pain a patient actually feels.

I commonly see patients who have significant pain but nearly normal x-rays.
I commonly see patients with extremely advanced arthritis on x-ray who state they have never had a day of thumb pain in their life.

This always surprises me, but it happens over and over again.

Our best estimates indicate only about 20% of those who develop thumb CMC arthritis (ie, everybody eventually) will actually notice physical pain from the condition.

This is why I always harp on the same point. I treat patients, I don’t treat x-rays.

Soft tissues

Another point that distinguishes CMC arthritis from other common sites of arthritis (eg, knee arthritis) is the soft tissue envelope that surrounds the CMC joint.

If you look at your hand palm up, you will notice that you can flatten your thumb so as to look at your thumbprint (see Figure 1). Now leave your palm where it is and swivel your thumb so that your hand forms a C-shape as if you were holding a can (see Figure 2). Now you are looking at your fingernail.

Figure 1

Figure 2

That is a 180-degree swivel of your thumb! And that motion happens entirely through the CMC joint.

So what does that tell us?

Similar to the shoulder (which allows near 360-degree rotation), the thumb CMC joint relies predominantly on the soft tissues surrounding the joint for stability.

This is why x-rays do not tell us the whole story. X-rays can only show us the bones. But this is a joint that functions based on the interplay between bones and soft tissues.

Remember this point. It has implications for our treatment discussion later on.

How does the thumb CMC joint typically function?

Let’s get a little more specific.

The thumb CMC joint is where two bones known as the thumb metacarpal and the trapezium (see Figure) meet.

Where the two bones come together actually looks somewhat like two horse saddles fitting together. Or two Pringle chips, if you prefer that analogy.

Many joints in the body form more of a ball and socket shape as they join (see Figure 4). The unique shape of the thumb CMC joint is what allows for that 180-degree motion we discussed above.

Figure 4
*Photo: Kcotton15, CC BY-SA 4.0*

But to remain stable (ie, not dislocate constantly), that bony anatomy is then heavily encased on all sides by thick strong soft tissues known as ligaments.

In many ways, this joint is brilliant. It is what allows us to pinch and do things with our hands that other animals cannot. Say, like go to the moon.

But every rose has its thorn.

The consequence of a joint that can swivel 180 degrees to facilitate pinch? The potential for instability.

Over the course of a lifetime of pinching, the ligaments will slowly stretch and wear out. As this happens over and over again, the joint will subtly rock back and forth and eventually grind away the cartilage padding between the bones.

In fact, each time you pinch between your fingertip and thumb, about 15 to 20 times the force you pinch with will get multiplied down and transmitted through your thumb CMC joint! As an analogy, imagine the torque on the feet of a construction crane lifting a heavy steel beam to the top of a building. Your thumb CMC joint is just like the anchor point of the crane.

Over time, these forces compound and the ligaments wear out. You end up creating shear forces across your joint that will eventually grind down the cartilage.

As I said earlier, nearly all of us will develop this arthritis, but only about 20% will develop associated thumb pain.

What are the typical symptoms of CMC arthritis?

The classic patient with thumb CMC arthritis will come to me after one to two years of increasing soreness at the base of their thumb.

When I say the base of the thumb, these symptoms are typically felt in the thick pad of muscles on the thumb side of your palm (see Figure 5). That is where the CMC joint lies. In fact, many people are not aware that there even is a thumb joint in this area.

Symptoms of pain and soreness typically increase with pinching activities, particularly activities involving narrow pinch. These would include motions such as turning a key or pulling up your socks. Or using your thumbs to text all day. This position of narrow pinch creates a shearing force at the joint that can be exquisitely painful.

Many patients also describe increasing hand weakness, difficulty opening jars, and loss of dexterity.

Another important symptom to look out for is any numbness or tingling in the thumb, index finger, or middle finger. Nearly 30% of patients who develop thumb base arthritis also develop carpal tunnel syndrome. Carpal tunnel syndrome is a pinching of the nerve that gives sensation to the thumb, index finger, and middle finger (read more here).

As you might imagine, losing grip strength from arthritis combined with losing sensation from carpal tunnel can lead to devastating dysfunction in the hand.

Finally, severe or long-standing cases of thumb CMC arthritis can also result in deformity. As the ligaments wear out, the joint will start to change its orientation, which ultimately narrows the palm.

A narrowed palm can make it look like you're developing a prominence over the back of your thumb joint (see Figure 6). A narrowed palm will also result in decreased grip strength and difficulty using the thumb. Lastly, it will eventually result in hyperextension of the other joints in your thumb to compensate for a narrowed grip (see Figure 6).

How is thumb CMC arthritis diagnosed?

This is one of those hand conditions that is relatively simple to diagnose. Patients will usually tell me a story similar to the symptoms above. In addition, they will be very tender when I press directly over the thumb CMC joint.

Additionally, there is a simple examination maneuver where I exert an axial push on the joint, and this is typically painful. I may even be able to feel subtle joint instability.

Finally, X-rays will show a narrowing of the space between the thumb metacarpal and trapezium bone.

Bone spurs are oftentimes visible around this joint as well. These are all typical x-ray signs of arthritis in the thumb CMC joint. More advanced images such as CT scans or MRI are not necessary.

What is the treatment for CMC arthritis?

As I've said many times before, I want to encourage you to take control of your health care.

Only you know how badly your thumb pain affects you and how your symptoms feel.

There are an array of treatment options available to you, all the way from observation to surgery. Be sure you choose the treatment strategy that best aligns with your goals and your symptoms. My only hope is to educate you so you can make your best choice.

It is important to remember that thumb CMC arthritis is not dangerous. Yes, it can be painful. And yes, it can progress over time. However, there's typically no rush to surgery. Again, focus on matching your symptoms to your treatment (and the treatment’s associated risk/benefit profile).

While the surgical option is generally very successful, it is also a significant surgery that will have you healing for many months. This all must be factored in when making a decision.

Hand therapy & bracing

When I first see a patient for arthritis, I will get them started right away on a hand therapy and bracing protocol.

Why?

Recall in part one when we discussed the importance of soft tissues in this joint.

You may also remember that only about 20% of people with thumb CMC arthritis actually develop pain.

These two factors are why therapy and bracing can be incredibly successful in relieving CMC arthritis pain.

Hand therapy with a certified hand therapist (CHT) accomplishes multiple goals:

Education about thumb mechanics and how to pinch to avoid pain
Develop a custom brace to protect you during painful activities
Strengthen the thumb to restore integrity to the joint-stabilizing soft tissues

If we can combine the benefits of each of the above, we stand a real chance at turning you from a patient with arthritis pain into a patient without. From the 20% who have pain, to the 80% who do not.

Even if all we do is cut your pain in half, that may be enough to keep you out of the operating room…often for good! As much as I love to operate, the goal should always be to avoid surgery if possible.

And remember. My goal isn’t for you to spend the rest of your life in a brace. This is about an initial investment in fighting down the pain. Thereafter, the brace should just be a tool to use intermittently when needed.

It is typically prudent to pair therapy and bracing with anti-inflammatory medications, especially early on. So much so that I’ve drawn up my own protocol. You can see my anti-inflammatory medication protocol linked here.

Steroid injections

If you end up in the unlucky cohort for whom therapy and bracing do not relieve your pain, steroid injections directly into the thumb CMC joint can be another viable option.

I prefer to be very targeted about exactly when I use a steroid injection. A steroid injection will not change your anatomy or improve the underlying disease of arthritis in any way.

Instead, it will effectively mask your symptoms for a short period of time by decreasing associated inflammation. Don’t get me wrong — this is absolutely a reasonable approach when trying to avoid or delay surgery for various reasons.

The results from this injection are highly variable. Some patients have a phenomenal relief of their pain, perhaps for many months or longer. Some patients unfortunately get minimal relief following their injection.

If injections fail, or the pain returns, I typically try to space out injections at least three months apart. And if two or three injections have failed, repeat injections eventually risk doing more damage than good to the integrity of the soft tissues. This is the point at which we may begin to discuss surgery.

What is the surgery for CMC arthritis?

There is a saying in surgery that goes something like this: “When there are 100 different ways to do a surgery, either none of them work or all of them work.”

I would put CMC arthritis surgery in this category. If you go down the rabbit hole of researching how a CMC arthritis surgery is done, you will quickly notice that there are nearly infinite technique variations.

The good news? They nearly all work extremely well.

What you might also notice about the different techniques is that they are all basically the same — with small variations.

For this discussion, we are going to focus on the most common type of surgery, known as a CMC arthroplasty (arthro = joint; plasty = restore/replace).

There are other types of surgery for CMC arthritis, but they are typically performed only in special cases (such as someone very young, or someone who puts extreme demands on their hands).

A typical CMC arthroplasty surgery can be broken down into two main steps:

Remove the trapezium bone
If you remember, the trapezium is a small wrist bone that lies next to the base of the thumb metacarpal bone. The joint between these two bones is what becomes arthritic when you have CMC arthritis. As you can imagine, removing one of these bones will cure the arthritis! There is no longer a bone to rub against the other.
Believe it or not, your hand can function extremely well without the trapezium bone. So, nearly all surgical techniques involve the removal of this bone.
Manage the void left behind
The second major step of any CMC surgery is to manage the gap that is left behind when we remove the trapezium bone. If we did nothing, the thumb metacarpal would eventually sink down into that space left behind and begin rubbing on the next bone.
Trapezium removal alone is actually all that was done when this surgery was first developed over 50 years ago. And most patients still did quite well even though the thumb metacarpal often collapsed into this space over time. As we have advanced, we have developed different techniques for managing this space. In fact, it is these different techniques that account for the wide variability in how this surgery is performed.

Surgical Technique

The classic technique to perform a CMC arthroplasty involves harvesting a tendon out of your forearm and using it to tie a sophisticated knot from your wrist through your thumb metacarpal in order to suspend it. This is called a ligament reconstruction with tendon interposition, or LRTI.

Recently, technology has advanced to allow us to suspend your thumb metacarpal, and maintain the space below, in a less invasive fashion. Again, there are numerous ways to do this, but they still all accomplish the same goal of preventing the thumb metacarpal from sinking into the void.

In my patients, I use a modification of a technique known as the “Internal Brace” (Arthrex - I have no affiliation with this company) suspensionplasty.

The surgical technique is actually quite an advanced discussion that warrants a deep dive in a separate article. We will wrap this description up here for now.

What is the recovery from CMC arthroplasty surgery?

As I've mentioned in other articles, it depends on what you mean by ‘recovery,’ as well as on which technique is used for your surgery.

One of the primary reasons I use my technique is to accelerate patient recovery. Rather than 2-3 months in a cast, my patients start moving their thumbs at 2 weeks.

Below is an outline of the typical recovery following my CMC arthroplasty.

Surgery until 2 weeks: Wear a post-operative splint full time, no thumb use or motion.

Beginning at 2 weeks: You will receive a removable splint made by a hand therapist and begin to work on gentle thumb range of motion exercises. No physical activity with the thumb.

Beginning at 6 weeks: Initiate light pinching activities with therapy and continue to work on range of motion. You will wean out of the brace for light activities.

Beginning at 8 weeks: Progress strengthening of the thumb with therapy and continue to use your brace less and less.

3-4 months: Return to heavy activities and/or impact sports. Most patients feel 80-90% of their former selves by this point. Occasional aches and pains, or a bad day here or there are still expected.

9 months to 1 year: This is ‘full’ recovery - when most aches and pains resolve.

Wrapping it up

As I mentioned above, there is far more to know about the specifics of thumb CMC arthritis and its treatment. There are special considerations if one develops CMC arthritis early in life or as the result of a traumatic injury. The above framework is the best way to think about ‘typical’ CMC arthritis.

Please stay tuned for a future deep dive into some of the nuances discussed above. And always feel free to send me any specific questions you may have that I didn't cover here.

In the meantime, I hope this article gives you the understanding you need to allow you to take back control of your health and choose a treatment that aligns with your symptoms and your values.

What Is Thumb CMC Arthritis? The Ultimate Guide For Patients