Thumb Basal Joint Arthritis
In a normal joint, cartilage covers the end of the bones and serves as a shock absorber to allow smooth, pain-free movement. In osteoarthritis (OA, or “degenerative arthritis”) the cartilage layer wears out, resulting in direct contact between the bones and producing pain and deformity. One of the most common joints to develop OA in the hand is the base of the thumb. The thumb basal joint, also called the carpometacarpal (CMC) joint, is a specialized saddle-shaped joint that is formed by a small bone of the wrist (trapezium) and the first bone of the thumb (metacarpal). The saddle shaped joint allows the thumb to have a wide range of motions, including up, down, across the palm, and the ability to pinch.