Trigger finger

[Jason Yan]

the finger that someone uses to shoot a gun

[Greta]

a disorder of the tendon of a finger that makes it difficult to straighten the finger once it is bent:

[Ernesto]

Trigger finger is locking of a finger in a bent position caused by inflammation of a tendon in the finger.
(See also Overview of Hand Disorders.)
The cause of trigger finger is unknown. Trigger finger is common among people with rheumatoid arthritis or diabetes. Repetitive use of the hands (as may occur from using heavy gardening shears) makes trigger finger more likely to develop.
In trigger finger, a finger becomes locked in a bent position. The finger locks when one of the tendons that flex the finger becomes inflamed and swollen, often with a noticeable round, raised area (nodule) in the palm. The inflammation and swelling may cause pain in the palm and in the base of the finger, especially when the finger is flexed and extended.
Normally, the tendon moves smoothly in and out of its surrounding sheath as the finger straightens and bends. In trigger finger, the inflamed tendon can move out of the sheath as the finger bends. However, when the tendon is very swollen, it cannot easily move back in as the finger tries to straighten, and therefore the finger locks. To straighten the finger, a person must pull on the finger to force the swollen area into the sheath—causing a sudden release and popping sensation similar to that felt when pulling a trigger.
A doctor makes the diagnosis of trigger finger by examining the hand and finger.