What is the cause of a " trigger thumb" or "trigger finger"?

Flexor tendon : What usually occurs in this problem is that the flexor tendon gets caught in on of the pulleys in the palm of the hand if mild it can be relieved with ice, nsaids and possible cortisone shots if it persists, you might need to have a release of the pulley performed to alleviate the catching.

Tendon nodule: A thickened area (nodule) of the flexor tendon to the affected finger can become "stuck" on the ligamentous pulleys that allow finger flexion and extension. You can force the nodule through the pulleys, and the "click" is called "triggering." anti-inflammatory drugs, steroid injections, or surgery to release the catch point are all possible treatments. Splinting can also help the nodule resolve.