Trigger finger (and trigger thumb) are conditions affecting the movement of the tendons as they bend the fingers or thumb toward the palm of the hand. This movement is called flexion.
The tendons that move the fingers are held in place on the bones by a series of ligaments called pulleys. These ligaments form an arch on the surface of the bone that creates a sort of tunnel for the tendon to run in along the bone. To keep the tendons moving smoothly under the ligaments, the tendons are wrapped in a slippery coating called tenosynovium. The tenosynovium reduces the friction and allows the flexor tendons to glide through the tunnel formed by the pulleys as the hand is used to grasp objects.
Triggering is usually the result of a thickening in the tendon that forms a nodule, or knob. The pulley ligament may thicken as well. The constant irritation from the tendon repeatedly sliding through the pulley causes the tendon to swell in this area and create the nodule.
What causes trigger finger? In children, triggering can be caused by a congenital defect that forms a nodule in the tendon. Type 1 diabetes has also been linked with trigger finger in children and teens. There are rare cases reported of trigger finger in children following a viral infection. In general, trigger finger tends to occur in younger children (most often under eight years old).
In adults, rheumatoid arthritis, partial tendon lacerations, repeated trauma from pistol-gripped power tools, or long hours grasping a steering wheel can cause triggering. Symptoms are similar in children and adults. Treatment is usually surgical release but there are some cases (especially viral-induced) when a wait-and-see approach can be adopted.