At first, the only sign of trouble may be soreness on the thumb side of the forearm, near the wrist. If the problem isn't treated, pain may spread up the forearm or further down into the wrist and thumb.

As the friction increases, the two tendons may actually begin to squeak as they move through the constricted tunnel. This noise is called crepitus. If the condition is especially bad, there may be swelling along the tunnel near the edge of the wrist. Grasping objects with the thumb and hand may become increasingly painful.