Definition
1) Definition - Tenosynovitis implies inflammation of a tendon and its enveloping sheath; deQuervain's tenosynovitis is a specific type of this entity which involves the tendons of two specific muscles on the thumb side of the hand - the abductor pollicis longus (APL) and the extensor pollicis brevis (EPB). These muscles are located in the forearm and their tendons travel across the wrist (through a "tunnel" termed the first dorsal compartment) on the thumb side to produce movement of the thumb. The walls of the affected tendon sheaths (basically protective coverings for the tendons) become thickened and inflamed, causing the symptoms described in the next section. The condition is 10 times more common in women, more often arises in the dominant hand, and usually occurs between the ages of 35 and 55.