Thumb Arthritis at the base of the thumb is more common in women and usually starts after age 40. The cause of this form of arthritis is unknown in most cases. Past
injuries to the joint, such as fractures or severe sprains, and generalized joint laxity may increase the chances of developing this form of arthritis at a younger age.
The most common symptom of thumb basal joint arthritis is a deep, aching pain at the base of the thumb. The pain is often worsened with activities that involve pinch, including opening jars, turning door knobs or keys, and writing. As the disease progresses, patients may experience pain at rest and at night, and patients often note loss of pinch and grip strength.
In severe cases, progressive destruction and mal-alignment of the joint occurs and a “bump” develops at the base of the thumb, which is caused by the thumb metacarpal moving out of position in relation to the trapezium. At this point, thumb motion becomes limited and the space between the thumb and index finger narrows, making pinch activities difficult.