Also called washerwoman's sprain, Radial styloid tenosynovitis, and de Quervain disease.
It is a tendinosis of the sheath or tunnel that surrounds two tendons that control movement of the thumb. The two tendons concerned are the tendons of the extensor pollicis brevis and abductor pollicis longus muscles.
These two muscles, which run side by side, have almost the same function: the movement of the thumb away from the hand in the plane of the hand—so called radial abduction (as opposed to movement of the thumb away from the hand, out of the plane of the hand (palmar abduction)).
The tendons run, as do all of the tendons passing the wrist, in synovial sheaths which contain them and allow them to exercise their function whatever the position of the wrist.
Evaluation of histological specimens shows a thickening and myxoid degeneration consistent with a chronic degenerative process. De Quervain is potentially more common in women; the speculative rationale for this is that women have a greater styloid process angle of the radius.
The cause of de Quervain's disease is not known. In medical terms, it remains idiopathic.
Some claim that this diagnosis should be included among overuse injuries and that repetitive movements of the thumb are a contributing factor, but there are no scientific data that support a link between hand use and de Quervain's. A common speculative cause or association today is typing on handheld devices, which has led to the condition being dubbed "Blackberry Thumb”.
Symptoms are pain, tenderness, and swelling over the thumb side of the wrist, and difficulty gripping.
Finkelstein’s test is used to diagnose de Quervain syndrome in people who have wrist pain. To perform the test, the examining physician grasps the thumb and the hand is ulnar deviated sharply. If sharp pain occurs along the distal radius (top of forearm, about 2cm below the wrist), DeQuervain's syndrome is likely.
Differential diagnosis includes ruling out:
• Osteoarthritis of the first carpo-metacarpal joint
• Intersection syndrome — pain will be more towards the middle of the back of the forearm and about 5cm below the wrist.