I developed what the doctor called a trigger finger but I don’t know how or why. I didn’t hurt it or do anything to cause the tendon to pull the way it did.

Trigger finger is a common tendon disorder of the hand. The flexor tendon pulls and causes your finger to fold or bend to the point that it locks. In most cases of trigger finger, it is idiopathic, which means that doctors don’t know why it happened, there is no known cause.