Most of the time, it originates from a recurring movement or forceful use of one's finger or thumb. Tendons are fibrous cords that attach muscle to bone. Each individual tendon is surrounded by a protecting sheath.  These injuries may bring about conditions like Boutonnière Deformity, characterised by a bent Center https://www.theorthopaedicandpainpractice.com/why-cant-i-straighten-the-tip-of-my-finger/