Osteoarthritis - Specifically in the thumb base joint (MCP -I)

Thumb base osteoarthritis is a troublesome condition located in the thumb joint. Here you’ll find more information about how this condition develops and its various symptoms. Feel free to read on to learn more.

What is thumb base osteoarthritis?

The thumb is the most frequently used part of the entire hand. For this reason, thumb base osteoarthritis (also known as thumb base wear) is common. With every movement, you may feel pain. The thumb base and the thenar area can become painful, and the pain may worsen with heavy use. The thumb may also lose strength, causing you to drop things more easily. Roughly one in three women over the age of 40 shows abnormalities in the thumb base joint on an X-ray, which confirms how common thumb base osteoarthritis is. Fortunately, it can be treated effectively.

What causes it?

The thumb base joint is formed by the trapezium (a small wrist bone) and the first metacarpal bone. This joint is not very stable. When the ligaments that connect these bones become loose, wear can occur because the joint no longer fits together properly. Pain often worsens with gripping motions, such as turning a key or opening a jar. In thumb base osteoarthritis, the thumb may take on an abnormal position where the thenar area collapses inward, and the rest of the thumb stretches outward. This often leads to swelling at the base of the thumb. X-rays can clearly reveal this abnormality. In some cases, a bone scan may be needed to confirm the diagnosis.

What symptoms occur?

Several symptoms may indicate thumb base osteoarthritis. Below are the most common ones:

• Pain when moving the thumb, such as when turning a key or opening jars
• Increased pain during thumb use
• Pain in the thenar region and thumb base of the hand
• Loss of grip strength, leading to dropping objects more frequently

How is thumb base osteoarthritis diagnosed?

Your doctor will ask you a few questions and perform a physical examination. Then, X-rays will be taken to determine whether thumb base osteoarthritis is present.

What treatments are available?

In cases of mild wear, rest, splinting, pain relief, and anti-inflammatory injections may be sufficient. If the osteoarthritis is advanced or symptoms persist, surgical intervention may be considered. Hand therapy may also be helpful.

In surgery, the damaged bone is removed and replaced with a tendon graft or prosthesis. This involves removing the trapezium bone. Using a piece of tendon or a prosthetic implant, a stable suspension of the thumb base is created. Another surgical option is the arthrodesis technique, in which the surgeon makes an incision on the palm side of the hand near the base of the thenar area.

After this procedure, the thumb can be used again, as surrounding joints compensate for the fixed joint. Laying the hand flat on a table may be more difficult, but this is offset by the relatively quick recovery, allowing you to use your thumb again soon.

A thumb brace can also be used in cases of thumb osteoarthritis. It helps reduce pain and limit further wear. These braces are typically made of rigid plastic and provide strong support.

Causes of thumb base osteoarthritis

The thumb base joint is formed by the trapezium bone and the first metacarpal bone, and is inherently not very stable. When the ligaments connecting these bones become loose, wear may develop because the joint no longer aligns well. Pain worsens with gripping motions like turning keys or opening jars. In thumb base osteoarthritis, the thumb often shifts into an abnormal position— the thenar region collapses inward while the rest of the thumb extends outward. This commonly results in swelling at the base of the thumb. The condition is clearly visible on X-rays, and in uncertain cases, a bone scan may be used.

Treatment of thumb base osteoarthritis

Mild wear can often be managed with rest, splinting, pain relief, and anti-inflammatory injections. If the condition is more advanced or persistent, surgery may be necessary. Hand therapy can also support recovery. During surgery, the affected bone is removed and replaced with a tendon graft or prosthesis. This includes removing the trapezium bone and replacing it with a stable suspension system using the graft. Another treatment method is arthrodesis. In this technique, the surgeon makes an incision on the palm side of the hand at the base of the thenar region. After the surgery, the thumb can function again, as nearby joints take over part of the movement. Laying the hand flat on a table may remain difficult, but this technique allows for a quicker recovery and return to function. A thumb brace may also be used for thumb osteoarthritis. It provides pain relief and helps reduce wear on the joint. These braces are typically made of rigid plastic material.