Osteoarthritis (OA) of the Base of the Thumb Book Now

Osteoarthritis (OA) of the Base of the Thumb

The carpometacarpal (CMC) joint at the base of the thumb enables rotational movement. Cartilage covers the bone surfaces in a healthy joint; this thus allows them to glide smoothly against one another.

Osteoarthritis (OA) of the base of the thumb is a common condition among adults over 40, with injuries such as fractures or sprains accelerating its development. Women are more likely than men to experience the symptoms.

Symptoms

Pain is the earliest sign of osteoarthritis in the thumb CMC joint, particularly when using the hand for tasks like opening jars, turning keys, or gripping a car door handle.

Repetitive or forceful hand movements, as well as prolonged pinching, place strain on the affected joint, triggering pain. Over time, thumb strength diminishes, and the joint at the base of the thumb may gradually shift out of alignment. Without treatment, continued use can result in total dislocation in the end. As the deformity worsens, joint mobility becomes increasingly limited.

During a physical examination, a noticeable bump at the base of the thumb may indicate subluxation or dislocation of the CMC joint. Applying direct pressure to the joint normally causes pain, and thumb movement while pressing on the joint may produce a painful grating feeling, a sign of cartilage erosion.

As osteoarthritis advances, the joint’s mobility declines further, making it harder to move the thumb outward, away from the finger and palm. As the base joint shifts further out of place, the other thumb joints may collapse when grasping objects. The prevalent collapse is known as a ‘zig-zag deformity,’ where the middle joint of the thumb bends backward, particularly during strong pinching motions.

Causes

The exact cause of osteoarthritis in the thumb CMC joint is unclear, but it is believed to result from ligament wear, leading to joint instability, metacarpal subluxation, and pain.

Secondary OA of the hand may develop due to underlying conditions, including:

  • Previous joint changes due to past trauma or injury, prior septic arthritis, and inflammatory conditions like rheumatoid arthritis (RA).
  • Metabolic disorders like calcium pyrophosphate deposition (CPPD) disease (pseudogout), Wilson disease, hemochromatosis, and Gaucher disease.
  • Endocrine disorders such as acromegaly, hypothyroidism, diabetes mellitus, and hyperparathyroidism.

Risk Factors

Several factors may increase the risk of developing osteoarthritis in the thumb CMC joint, including:

  • Female gender
  • Age (over 40 years)
  • Menopause
  • Genetic predisposition to arthritis
  • Being overweight (obesity)
  • Ligamentous laxity
  • Occupational factors like repeated thumb use or weighty manual labour
  • Previous joint injury

Notably, knuckle cracking is not linked to an increased risk of osteoarthritis in the hand.

Diagnosis

Diagnosis of thumb CMC osteoarthritis is based on a physical examination and patient history. A doctor will assess symptoms, check for tenderness, swelling, and deformity at the base of the thumb, and evaluate thumb movement and strength. When moving the joint, a characteristic grinding sensation (crepitus) may indicate cartilage wear. X-rays can confirm the diagnosis by revealing joint space narrowing, bone spurs, or misalignment.

Treatment Options

Non-surgical treatments:

The treatment for OA of the base of the thumb depends on the severity of the symptoms. In the early stages, at-home remedies may help manage pain. These remedies include:

  • Ice and heat therapy: Applying ice to the thumb joint for 5–15 minutes several times a day can reduce swelling. Alternatively, using a heating pad for the same duration may help relax the joint.
  • Pain medication: Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Advil®) or aspirin can minimise swelling and inflammation. Acetaminophen (Tylenol®) may also be an option.
  • Splinting: Wearing a soft, supportive splint can assist in stabilising the thumb, limiting movement, and providing rest for the joint. Splints can be worn intermittently for added support throughout the day or at night.

Since this is a progressive condition, symptoms may worsen with time despite at-home treatments. A healthcare provider may suggest steroid injections to reduce pain and inflammation if this occurs. These injections provide temporary relief, typically lasting several months, but their effectiveness decreases with repeated use.

Surgical treatments:

Surgery is considered when pain becomes severe and non-surgical treatments are no longer effective. Several surgical procedures are available, and the best option depends on the condition’s severity and individual factors.

Metacarpal osteotomy

This procedure involves cutting and repositioning the metacarpal bone at the thumb base to relieve pain and improve function. It is typically recommended for patients with mild or early-stage osteoarthritis.

Joint fusion (arthrodesis)

In this procedure, the arthritic joint is taken out, and the affected bones are attached to a single bone. It is most commonly performed in younger and middle-aged men who engage in manual labour. This is because it helps preserve thumb strength better than other surgical options.

Trapeziectomy

This procedure involves removing the trapezium, a small bone at the thumb base, to reduce pain and improve function. In some cases, a wrist or thumb tendon is used to help stabilise the thumb. A temporary pin may also be placed to provide additional support during healing. Trapeziectomy is the most commonly performed surgery for thumb CMC osteoarthritis in the UK.

Joint replacement

This is a surgical procedure that involves removing all or a portion of the damaged thumb joint and substituting it with a synthetic implant. This procedure aims to restore joint function, reduce pain, and improve thumb mobility.

Bottom Line

As osteoarthritis of the base of the thumb progresses, simple tasks can become increasingly difficult and painful. While this condition is common, it can significantly impact daily activities. If the pain becomes too much to manage, consult a healthcare provider. They can discuss treatment options to relieve discomfort and help you adapt to everyday tasks.

Book an appointment today to explore the best approach for managing your symptoms.