There is a joint at the base of the thumb called the basal joint or CMC (carpometacarpal) joint. This joint allows the thumb to swivel and pivot in order to touch the fingers, pinch, and pick up objects.

Osteoarthritis is fairly common in this joint because it gets used so much in daily activities. People get arthritis in this joint when they don't have arthritis anywhere else. Injuring the thumb puts the joint at increased risk for arthritis later.

Pain at the base of the thumb during pinching and gripping is common. Loss of motion can also occur. Many people have a weak pinch grip.