The thumb base refers to the first carpometacarpal joint (1st CMCJ) where the metacarpal and trapezium bones meet. This joint is sometimes called the trapeziometacarpal joint (TMJ). 

With advancing years, the normally smooth cartilage that lines both surfaces of the joint can become thinned and roughened, which causes the joint to narrow. This ‘wear and tear’ (or degenerative) type of arthritis is called osteoarthritis and is a normal part of ageing (like hip and knee arthritis). When symptomatic, osteoarthritis produces pain with activity (and sometimes at rest), stiffness and reduced movement.

The thumb base is predisposed to developing arthritis due to its wide range of movement, including opposition, whereby the thumb rotates to meet the tips of the other fingers. The thumb is also responsible for 70% of hand function, and most activities requiring grip (whether holding a pen, lifting a kettle or wielding a hammer) will transmit high forces through the thumb base and contribute to wear and tear over time.

Less commonly, thumb base arthritis can follow a previous trauma or injury of the thumb base (1st CMCJ), for example a fracture (break) or dislocation. This ‘secondary osteoarthritis’ is more often seen in younger adults.

Thumb base arthritis (osteoarthritis) is a normal part of ageing, just like hip and knee arthritis. The condition is more common in women, tends to run in families (there is a genetic component), and can be related to prolonged heavy and repetitive manual work or hobbies.

Plain radiographs (X-rays) will demonstrate signs of thumb base arthritis in around 60% of women over the age of 60 years; however, many will experience no pain despite changes on X-rays.

Conditions such as hypermobility can also predispose to thumb base arthritis due to ligament laxity and increased movement at the thumb base.

In a younger population, an injury of the thumb base (like a fracture or dislocation) can lead to ‘secondary osteoarthritis’ in future years.

Some of the potential symptoms of thumb base arthritis are listed below.

Typically present:

• Pain at the base of your thumb (where your thumb connects to your wrist).

• Pain that worsens with grip, especially when opening bottles or jars.

• Tenderness at the thumb base.

Sometimes present:

• Thumb stiffness (reduced movement when compared to previous).

• Weakness of grip (usually due to pain).

• Pain in the wrist.

• Muscle wasting at the thumb base (muscles appear smaller).

• Changes in the shape of your thumb, including a ‘zig-zag’ alignment (with a bump at the thumb base and increased extension at the middle joint of the thumb).

It is important to correctly diagnose thumb base arthritis and exclude other causes of pain in the region of the thumb base; such as De Quervain’s syndrome (tendonitis), wrist arthritis or scaphotrapeziotrapezoid joint (STTJ) arthritis.

The diagnosis is usually made on the history (your symptoms), clinical examination and plain radiographs (X-rays).

In most cases, the treatment for thumb base arthritis is non-surgical, and most people will never require surgery for this condition.

• Non-surgical treatment options include simple painkillers, avoidance of painful activities, a thumb splint and hand therapy. It may take weeks or months to notice a gradual improvement and return to function. A steroid injection (e.g. cortisone) can be a very effective treatment; however, the pain-relieving effect will differ between individuals and will usually wear off with time (a good and common response would be 3-6 months of improved pain). 

• Surgical treatment options include trapeziectomy and, for some, thumb base replacement (or fusion). Trapeziectomy is the most common operation and involves removing the trapezium bone (a small wrist bone at the base of your thumb). This operation removes one of the two arthritic joint surfaces that is causing your pain. Thumb base replacement is a newer treatment (Matthew uses the Touch® implant by Kerimedical); however, it is not suitable for all types of thumb base arthritis. Other surgical options, such as thumb base fusion or arthroscopy (keyhole) treatment, are infrequently used.

Matthew offers all the above treatments. At the current time, Matthew performs thumb base replacement in the NHS only.

Thumb base arthritis surgery is usually performed under general or regional anaesthesia. Click here for an overview of the different types of anaesthesia. and the general risks of hand surgery.

The specific risks associated with the different thumb base operations will be discussed if surgery is an option.

You can read more detailed information about thumb base arthritis on the Lothian Hand Unit website.

The British Society for Surgery of the Hand (BSSH) has an informative webpage on thumb base arthritis, which can be downloaded as a patient information leaflet PDF.