Arthritis affecting the basilar joint of the thumb, or the first carpometacarpal joint located near the wrist bone, is called Basilar joint arthritis.

A form of osteoarthritis, Basilar joint arthritis affects women more commonly than men. It generally occurs after the age of 40, as a result of many of the same joint conditions prompting osteoarthritis of other joints – joint instability, cartilage deterioration, wear and tear.

The unique shapes of the small bones of the thumb permit its movement in and out of the plane of the palm to oppose the other fingers. The stability of the carpometacarpal joint of the thumb depends on several small ligaments, which allow movement but remain close to the joint surfaces. If the ligaments loosen and permit too much sliding of the joint surfaces, increased wear on the joint cartilage may occur – leading to arthritis. A fracture or injury can also lead to joint dysfunction and deterioration, ultimately leading to arthritis as well.

Inflammation may occur as joint degeneration progresses. Pain is prominent when pressure is applied to the joint in pinching and grasping activities. If left untreated, joint surfaces are eventually destroyed and bony spurs may develop around the joint. In severe cases, there may be complete joint destruction, an inward collapse of the metacarpal, and deterioration around the trapezium. Other joints may also become affected as they react to the changes.

Basilar joint arthritis will produce pain that progresses over time, eventually discouraging use of the thumb. This correspondingly results in joint weakness and muscle loss. Upon examination, there may be swelling at the base of the thumb as a result of joint inflammation.

After assessing a patient’s history and a physical examination of the thumb, an X-ray may help show the degree of joint damage. And a series of X-rays can help determine the rate of progression.

Treatment is determined based on the affect the arthritis has had on a patient’s joint at the time of diagnosis. It may involve conservative treatment – including anti-inflammatory medications such as aspirin or ibuprofen, refrain from inflammatory activity, corticosteroid injections, rehabilitation and occupational therapy, as well as splinting of the thumb to help support it – reducing pain and preventing deformity.

In more advanced cases arthroplasty is indicated in order to remove the damaged joint surfaces and create a substitute joint – eliminating pain, and improving strength and range of motion.

The earlier the diagnosis, the greater the chance of preventing irreversible damage.