Basal joint arthritis (otherwise known as "thumb arthritis" or "CMC arthritis") is a condition caused by the development of osteoporosis in the carpometacarpal (CMC) joint, where your wrist meets the bone at the base of your thumb. It usually develops over a period of years and is one of the most common joints in which arthritis occurs in the hand. Women over the age of 40 are particularly susceptible to the condition, outnumbering men who suffer from it by a ratio of 10 to 1. Other factors such as genetics, being overweight, previous fractures or dislocations, or excessive and repetitive use (such as in assembly line work) may also be predisposing conditions. Common symptoms of basal joint arthritis are described below.
Pain
Osteoarthritis is degenerative; therefore, it causes the cartilage that normally covers the ends of the wrist and thumb bones at the carpometacarpal joint to wear down. The bones eventually start to rub against each other, causing friction, joint damage and pain.
Pain frequently occurs when attempting to pinch or grasp an object with the thumb and forefinger. Other activities that involve applying pressure with the thumb, such as pulling on a zipper or turning the top of a jar, may also cause pain. In severe cases and over time, pain may occur independent of activity.
Rigid and non-rigid splints, arthritis medications or a limited number of cortisone injections may help to alleviate pain in mild to moderate cases. Surgical reconstruction, realignment, fusion or arthroscopy may be required to ease pain in severe or treatment refractory cases.
Swelling and Tenderness
Inflammation can occur, causing swelling and stiffness at the base of the thumb. The area may also feel warm, tender and sensitive to touch.
Misalignment and Limited Mobility
In severe cases of Basal Joint Arthritis, the joint may become progressively malformed to the point that the thumb bone (metacarpal) moves out of the CMC joint, giving the thumb an enlarged and bony appearance. This misalignment results in limited motion of the thumb and decreased ability to pinch, grab and apply pressure with the thumb. The joint above the CMC may then loosen to compensate, causing it to hyperextend. In very severe cases, the thumb may sink into the palm, causing what is known as a zigzag deformity where the middle joint hyperextends and the last joint flexes.
