Trigger finger results from tendon inflammation. The tendons that bend the finger enter a tunnel system in the palm. For reasons that are not well-understood, the tendon can become inflamed which is felt as a nodule in the palm. When the finger is bent, the tendon gets stuck and the finger is locked in a bent position.
Treatment typically requires an injection of cortisone. One or two injections gives relief in most cases. Approximately 20% of people will need a minor surgery to open the tunnel. In diabetic patients, the injections are less effective and work only about 50% of the time.