De Quervain's tenosynovitis is a painful condition that affects the tendons in your wrist. It occurs when the 2 tendons around the base of your thumb become swollen. The swelling causes the sheaths (casings) covering the tendons to become inflamed. This puts pressure on nearby nerves, causing pain and numbness.
De Quervain's tenosynovitis is swelling of the tendons that run along the thumb side of the wrist and attach to the base of the thumb. This occurs when the tendons are constricted by the sheath that they run through to get from the wrist to the hand.
This condition can cause pain and tenderness along the thumb side of the wrist. This is particularly noticeable when you are: