Trigger Finger / Thumb

As your fingers bend and straighten, the tendons move in and out of a tunnel within each digit (finger or thumb). The tunnel has an entrance ('mouth') and an exit.  The entrance lies under the transverse skin crease in the palm at the base of the fingers. The exit is situated almost at the end of each digit.

The tendons which bend the fingers are not a uniform shape like an electricity cable, but variously have wider portions, thinner portions and, often, well defined lumps or 'nodules'. Sometimes, these nodules enlarge slightly which then makes it difficult for the tendon to easily slip into the mouth of its tunnel without some resistance. It is this sudden 'snap' as the tendon nodule is pulled into the tunnel that is the hallmark of a trigger finger.

Sometimes, the nodule can be so large that it is impossible for it to get into the tunnel. In these situations, the trigger finger is described as 'locked'.

Trigger finger is usually the result of some inflammation of the lining of the tunnel or the covering of the tendon. This produces a mechanical 'mis-match' in the size of the tendon and its tunnel. For that reason, trigger finger is often encountered in rheumatoid arthritis, but it is also seen in diabetes and patients with a history of thyroid gland trouble.

Most cases of trigger finger respond well to an injection of steroid (cortisone) around the entrance to the tendon tunnel. The triggering starts to resolve around 48 hours after the injection and may disappear completely. If the triggering returns, or the injection fails, surgical division of the entrance to the tunnel under local anaesthetic will provide a permanent cure. The operation takes around 5 minutes and leaves a small scar in the palm. The only risks of the operation are a 1% risk of infection, and a degree of stiffness of the middle finger joint for a few weeks. Advice to passively stretch the finger fully straight in the days after surgery will usually be given.

Further information on trigger finger is available using these links:

Trigger finger BSSH info

Trigger finger info

Trigger finger NHS info