Arthritis of the base of the thumb
Any condition that damages a joint is called arthritis. In a normal joint, cartilage covers the ends of the bones and allows them to move smoothly and painlessly against one another. With osteoarthritis (also called degenerative arthritis), the cartilage layer wears out and the bones rub against each other. As the cartilage layer continues to wear out, symptoms of arthritis develop and the joint is eventually destroyed.
In the hand, the second most common joint to develop osteoarthritis is the joint at the base of the thumb, known as the basilar joint, between the thumb metacarpal and a bone of the wrist called the trapezium.
Arthritis in the basilar joint of the thumb is more common in women than in men. It usually starts after age 40. Past injuries to this joint such as fractures or sprains may increase the chances of developing this type of arthritis.
Symptoms of Arthritis of the base of the thumb
The first symptom of basilar joint arthritis is pain with activities that involve gripping an object with the thumb and fingers (pinching). These activities could include opening jars, turning door knobs, opening car doors, and turning keys. Heavy use of the thumb may also cause pain in the basilar joint, as can changes in weather, such as a change in humidity or temperature. As the disease worsens, less activity is needed to produce pain. Pinching strength decreases and swelling may develop when using the thumb. As the arthritis continues to worsen, the basilar joint begins to look bigger and “out-of-joint.” At this point, movement of the thumb becomes limited.
Close inspection will sometimes show a lump at the base of the thumb. Forcing the thumb firmly against the wrist bone while moving the joint will usually produce pain and may produce a gritty feeling indicative of the bones are rubbing against each other.
Treatment of Arthritis of the base of the thumb
The pain of early basal joint arthritis will usually respond to non-surgical treatment: limiting movement of the thumb (placing a splint on the thumb) and using medicine (oral or local injection) to decrease swelling and pain. Patients with more severe cases may require surgery.
There are a number of surgical options available including removing one of the bones at the base of the thumb, fusing the joint or replacing the joint.