Making the Diagnosis
Doctors have a wide range of tests to check for damage to different tendons. De Quervain's syndrome, for example, is detected by the test known as Finkelstein's sign. By placing the affected thumb across your palm and closing your fingers on it, you then flex your wrist in all directions. If there's pain at the top of the wrist just behind the thumb, then it's a clear indication of De Quervain's syndrome. Similar tests exist for all types of tendinitis.
Your doctor will also want to know if the problem is strain- or injury-related, or if some other disease is the cause. Most other diseases can be ruled out using simple blood tests. Your doctor may also recommend imaging tests such as an ultrasound or a magnetic resonance imaging (MRI) scan.