De Quervain’s tendinitis occurs when the tendons around the base of your thumb become irritated. The irritation causes swelling and pain along the thumb side of your wrist. You have probably noticed the pain most when forming a fist, grasping objects, when turning your wrist or picking up your child, feeding your baby, or putting your seat belt on. It can be a sharp grabbing pain at the base of the thumb, or a dull aching feeling - or you might experience both types of pain.