Basilar Thumb Arthritis

Basilar thumb arthritis, also known as thumb carpometacarpal (CMC) joint arthritis or trapeziometacarpal arthritis, is a degenerative condition that affects the joint at the base of the thumb where the thumb meets the wrist. This joint is formed by the trapezium bone of the wrist and the first metacarpal bone of the thumb and is shaped like a saddle, allowing the thumb its wide range of motion.
This specialized joint allows you to pinch, grasp, twist, and grip objects. Because it is heavily used in daily activities, it is particularly susceptible to osteoarthritis, a condition in which the cartilage that cushions the joint gradually wears away. As cartilage deteriorates, the bones can rub against each other, leading to pain, stiffness, and progressive joint damage.
Basilar thumb arthritis is most commonly seen in women over the age of 40, but it can affect men and younger individuals, especially those with prior injuries or repetitive thumb use.

Common symptoms include pain at the base of the thumb, especially when pinching, gripping, or twisting objects. Patients may also experience swelling and tenderness at the thumb base, weakness or reduced grip and pinch strength, stiffness, and decreased range of motion. Many people have difficulty performing daily tasks such as opening jars, turning keys, writing, or using tools. As the joint degenerates, a visible bump or deformity may develop at the base of the thumb.

Basilar thumb arthritis is typically progressive, meaning symptoms may worsen over time without treatment.

Diagnosis begins with a detailed medical history and physical examination. Your physician will evaluate your symptoms, activity level, occupation, and any history of hand or thumb injury.

During the exam, the stability of the thumb CMC joint is assessed. A commonly used maneuver is the CMC grind test, in which the thumb metacarpal is compressed and rotated against the trapezium bone. Pain or grinding during this test suggests arthritis.

The metacarpophalangeal (MCP) joint above the CMC joint is also examined, as advanced CMC arthritis can cause compensatory instability or hyperextension at this joint.

X-rays are obtained to evaluate the severity of arthritis and may show joint space narrowing, bone spurs, bone-on-bone contact, joint subluxation or deformity, and involvement of neighboring joints.

Many patients experience significant relief with conservative, non-surgical treatments, especially in early or moderate stages. Activity modification can reduce joint stress by limiting movements that cause pain, such as repetitive pinching or gripping. Medications such as nonsteroidal anti-inflammatory drugs (NSAIDs) can help reduce pain and inflammation. Ice therapy can help decrease swelling and discomfort when applied to the thumb base.

Splinting and bracing support the base of the thumb and reduce joint stress. Ideal splints stabilize the CMC joint while allowing wrist and finger movement. Hand therapy with an occupational or hand therapist can improve strength, flexibility, and joint protection techniques to reduce strain on the thumb. Corticosteroid injections can provide temporary pain relief and reduce inflammation. Relief may last several months, but injections are not a permanent solution and may become less effective over time.

When symptoms persist despite conservative treatment, surgery may be recommended. Several surgical techniques are available, and the best option depends on arthritis severity, patient age, activity level, and functional goals.

Common surgical procedures include trapeziectomy with ligament reconstruction and tendon interposition (LRTI), suspensionplasty techniques to stabilize the thumb, joint fusion to eliminate painful motion, thumb CMC joint replacement with implants, and arthroscopy in select cases for minimally invasive treatment. These procedures are highly effective at relieving pain and improving function.