There are two common causes of pain on the thumb side of the wrist. The most common cause is a particular kind of tendinitis with a peculiar name: DeQuervain’s tenosynovitis. The diagnosis is largely made on the basis of history (especially of repetitive wrist motion such as crochet or lifting a newborn or remodeling a house). In addition there is a sign on physical examination which is quite reliable. It’s a maneuver called the Finklestein’s test. This if positive, is almost diagnostic of this problem.
Fortunately, this usually (but not always) readily responds to a single cortisone injection.
Another problem which can cause similar symptoms and which can occur in conjunction with DeQuervain’s, is basal joint arthritis of the thumb. This can be called by a number of other names (CMC joint arthritis for example) but examination in addition to x-rays is frequently diagnostic. Treatment includes an injection, rest with various kinds of splints, and ultimately if these are unsuccessful, surgery.
The exact type of surgery depends on a number of variables but it is done as an outpatient and has a high degree of success.