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Basal Joint Osteoarthritis

This condition is a degeneration of cartilage in the joints at the base of the thumb, collectively called the basal joint. The main component of the basal joint is the thumb carpometacarpal (CMC), joint. This joint, which allows the thumb to pivot and swivel, can wear out even early in life.

This condition is caused by aging, repetitive motions, and wear and tear that occurs during normal use of the hand. It typically results from weakness of the volar beak ligament, which normally helps maintain joint stability. When this ligament weakens, the thumb can begin to move abnormally and the joint becomes irritated and inflamed. Gradually, the cartilage that lines the joint degenerates, allowing bone to rub directly against bone. As the CMC joint degenerates, other articulations of the basal joint can become affected.

The most common symptom is pain at the base of the thumb, especially when gripping or pinching. A grinding sensation may be felt when the thumb is moved. The thumb may also become weak and stiff. As the condition worsens, the joint may become deformed, and a bump may form where the thumb meets the wrist.

The doctor will order x-rays of the wrist and hand to diagnose this condition. MRI or CT scans are usually not required.

Treatment options include cortisone injections, non-steroidal anti-inflammatory medications, use of a splint or brace, exercise, and modification of daily activities. Surgery may be needed.

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