Elbow Issues

Arthritis of the Thumb

Causes
Arthritis is a condition in which a joint becomes inflamed (red, swollen, hot, and painful).Degenerative arthritis is a condition in which a joint wears out, usually slowly over a period of many years. Doctors sometimes also describe this same condition as degenerative arthrosis. It is also called osteoarthritis.

Injury to a joint, such as a bad sprain or fracture, can cause damage to the articular cartilage. An injury the CMC joint of the thumb, even if it does not injure the articular cartilage directly, can alter how the joint works. After a fracture of the thumb metacarpal, the bone fragments may heal in slightly different positions. The joints may then line up differently. This is also true when the ligaments around the CMC joint are damaged by a sprain. When an injury results in a change in the way the joint moves, the injury may increase the forces on the articular cartilage surfaces. This is similar to any mechanical device or machinery. If the mechanism is out of balance, it tends to wear out faster.

Over many years this imbalance in the joint mechanics can lead to damage on the articular surface. Since articular cartilage cannot heal itself very well, the damage adds up. Eventually, the joint is no longer able to compensate for the increasing damage, and it begins to hurt. Damage has occurred well before the pain begins.

Symptoms
Pain is the main problem with degenerative arthritis of any joint. This pain occurs at first only related to activity. Usually, once the activity gets underway there is not much pain, but after resting for several minutes the pain and stiffness increase. Later, when the condition worsens, pain may be present even at rest. The most noticeable problem with CMC joint arthritis is that it becomes difficult to grip anything. It causes a sharp pain at the base of the thumb in the thick part of the heel of the hand.

When the articular cartilage starts to wear off the joint surface, the joint may make a squeaking sound when moved. Doctors refer to this sound as crepitus. The joint often becomes stiff and begins to lose motion. Moving the thumb away from the palm may become difficult. This is referred to as a contracture.

Osteoarthritis may cause the CMC joint of the thumb to loosen and to bend back too far (hyperextension). If the middle thumb joint (MCP joint) becomes flexed and the furthest thumb joint also becomes hyper-extended, the deformity is named a thumb swan neck deformity. A similar finger deformity sometimes occurs in people with finger arthritis.