Trigger finger is a common problem that causes pain and snapping of the tendons in the fingers. The problem that occurs in a patient who has trigger finger is due to the tendons of the fingers, and the sheath in which these tendons live.
The name trigger finger is from the symptom of triggering or snapping. This occurs when relaxing a fist, the affected trigger finger remains flexed. When enough force has been gathered, the trigger finger will suddenly extend, like pulling a trigger.
The tendons in your fingers are like ropes that attach to the ends of your fingers. When your forearm muscles contract, the tendons pull the fingers into a fist. The tendons run part of their course through a sheath called the flexor tendon sheath. In patients who have a trigger finger, this mechanism of movement of the tendon within the sheath is not smooth.
Trigger Finger Causes
The cause of trigger finger is often unclear, and can seemingly appear from nowhere. It can occur in one or more fingers, and can occur at different times in different locations. Trigger finger results from a discrepancy between the size of the tendon and the size of the entrance to the tendon sheath. This discrepancy can be the result of localized inflammation or a nodular swelling on the tendon itself.
When the size discrepancy between the tendon and the tendon sheath reaches a critical point, the tendon will experience resistance from the tendon sheath. At first, this is felt as a snapping of the trigger finger when relaxing a fist. If the condition worsens, the trigger finger may need applied pressure from other fingers to straighten, or may not straighten at all.
Trigger finger treatments may consist of simple steps, injections, or surgery. Often people start off with something simple, and if the symptoms persist or return, a surgery may be recommended.
Saldana MJ. "Trigger Digits: Diagnosis and Treatment" J Am Acad Orthop Surg July/August 2001; 9:246-252.