My thumb won't bend what's wrong with it?

Trigger thumb is: The most common conditon that leads to this.. In a trigger thmb the flexor tendon gets stuck as it tries to glide along the undersurface of the thumb to flex the ip joint. The tendon stops and the joint too. Often the stiffness is preceded by a period where there was clicking. Many times corticosteroid injections work well for this but surgery is needed too less often.