Pain along the back of the thumb, directly over two thumb tendons, is common in de Quervain's.
The condition can happen gradually or start suddenly. In either case, the pain may travel into the thumb or up the forearm.
It may be hard and painful to move your thumb, particularly when pinching or grasping things. Some people also have swelling and pain on the side of the wrist at the base of the thumb. The pain may get worse when you move your thumb or wrist.