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Stenosing tenosynovitis, commonly known as trigger finger or trigger thumb, involves the pulleys and tendons in the hand that bend the fingers. The tendons work like long ropes connecting the muscles of the forearm with the bones of the fingers and thumb. In the finger, the pulleys form a tunnel under which the tendons must glide. These pulleys hold the tendons close against the bone. The tendons and the tunnel have a slick lining that allows easy gliding inside the pulleys.
Trigger finger/thumb happens when the tendon develops a knot or swelling of its lining. When the tendon swells, it must squeeze through the opening of the tunnel that causes pain, popping, or a catching feeling in the finger or thumb. When the tendon catches, it produces inflammation and more swelling. This causes a cycle of triggering, inflammation, and swelling. Sometimes the finger becomes stuck (locked) and is hard to straighten or bend.
Trigger finger/thumb may start with discomfort felt at the base of the finger or thumb. A thickening may be found in this area. When the finger begins to trigger or lock, the patient may think the problem is at the middle knuckle of the finger or the tip knuckle of the thumb. This disorder is often associated with using tools that have handles with hard or sharp edges or whose handles are too far apart for the user’s hand. Meat packers, poultry workers, electronic assemblers, and carpenters are at risk of developing trigger finger.