THUMB OSTEOARTHRITIS

what is it?

Arthritis at the base of the thumb is known as 1st CMC joint (Carpometacarpal) osteoarthritis. It is 8 times more common than arthritis of the knee and can lead to difficulty with many every day tasks and serve pain.

Osteoarthritis of any joint (OA) is caused by wear and tear to the smooth cartilage covering the ends of the bones where they articulate against each other during movement. It is usually easy to spot OA in the small finger joints as it looks like bumps on the sides of the fingers. 

Although wear and tear is usually seen in older age the degree and progression of the wear and tear is affected by other things such as occupation and any previous injury to the joint such as a fracture or dislocation, perhaps in childhood. For this reason, CMC OA is often seen more in men under age 50 and more in women over age 50 with 1 in 4 women affected.

In some cases the disease of the cartilage is very advanced and treatment will require a multidisciplinary team to work with you to decide what treatment to give. This could mean steroidal injections in the short term and surgery as a longer term solution. Surgery may mean fusing or replacing the joint or removing a bone to make space.

How is it diagnosed?

An x-ray is the most common way to see if there has been erosion of the joint surfaces and will also help to confirm the current stage of arthritis and if more than one joint is affected. Blood tests are not effective at confirming OA.

Unfortunately, the beginnings of joint changes start in the ligaments and muscles surrounding the joint, and these don't show up in a normal x-ray. Ligaments and muscles are very important for joint stability and if they are sending or receiving incorrect information about their position ( called proprioception) it puts increased pressure on the joint bones. This eventually leads to bone on bone and later the development of thumb OA. 

As X-rays do not show if ligaments or muscles have poor proprioception, people may be incorrectly advised to accept pain as part of growing old and that nothing can be done to prevent it or slow it down. In fact, the opposite is the case. Appropriate treatment with exercise can improve muscle and ligament strength and decrease the risk of developing thumb OA in most cases.

Therefore, having an X-ray does not reliably confirm the presence of early soft tissue changes and does not identify the risk of future development of OA in younger age groups.

Complications

The thumb is used in 70% of hand actions and is the most used digit in the hand. Because of so much use the cartilage gradually becomes thin between the base of the thumb and a small bone near the wrist called the Trapezium. In advanced OA the Trapezium touches other small wrist bones and this impacts further on wrist movement and produces severe pain and stiffness.

CMC joint stiffness and a gradual pulling of the thumb toward the palm (called "Zedding"), forces other nearby joints to compensate by over stretching. As a result, they can become unstable too under the pressure, accelerating the development of CMC OA.

Secondary destruction of the joint surfaces occurs when Osteophytes grow. These are tiny bumps formed by bone overgrowth in a effort by the body to fill in the thin cartilage. Unfortunately they cause additional pain as the bones grind together and they reduce the range of movement available in the joint. 

What can Hand Kinetics do?

Early: As soon as a person of any age notices thumb weakness and pain it is important to learn specific exercises to strengthen the affected ligaments and muscles around the thumb. This will help to prevent or slow down the development of OA.

Strong muscles act as their own splint by creating space between the joint surfaces so the cartilage is protected from unnecessary wear and erosion.

Middle: Treatment should be aimed at preventing further wear and tear, however, this will not turn back the clock on the damage already done during the early stage when the joint was unstable.

Pain and weakness can be helped by using energy saving ways of doing activities to prevent unnecessary effort for the joints or in some cases clever small aids can do the job for you. This way you can save energy for more fun activities. 

Steroidal injections are often administered by GP’s and are helpful in the short term but are not recommended more than three times. This emphasises the importance of learning alternative approaches to manage pain and prevent thumb deformity. 

Late: In more advanced stages wearing a small device around the thumb for daily activities will help to give the thumb some security and reduce pain. There are a variety of splinting options available on the open market but it can be confusing choosing between something soft or hard for support without the correct advise. Hand Kinetics can show you several options and make you a personalised thumb support depending on the activities you plan to do with it on.

In some cases, surgery may be considered. This involves either replacing the joint (Arthroplasty) or fusing it (Arthrodesis).