Trigger finger results when a flexor tendon in your palm or finger catches on a pulley and can no longer slide to flex the finger. A common condition that can be disabling, trigger finger can be caused by a diseased pulley or a swollen tendon.
At intervals, pulleys keep the tendons in place by tunnelling through ligaments that run along the bone. Trigger finger straightens with the snap of a finger, like pulling and releasing a gun trigger.
In most cases, no tests are necessary to confirm the diagnosis. An ultrasound may be required if the diagnosis is ambiguous.