Boutonnière deformity (BD) prevents you from straightening your finger. The disorder affects the finger’s system of tendons. The tendons allow you to flex and straighten your finger.

Tendons in Finger
Finger Tendon
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In BD, the tendon on the top of the finger (called the central slip) is torn or cut from the other tendons. This creates a tear that resembles a buttonhole (or boutonnière in French). The middle joint is forced down and the fingertip bends back. The tendons on this part of the finger are flat and thin. They are prone to injury. If you have BD in the thumb, it affects a joint called the metacarpophalangeal (MCP).

BD can be caused by:

  • A powerful blow to the finger
  • A cut to the finger’s central slip
  • An injury to the middle finger joint—called the proximal interphalangeal (PIP) joint
  • A severe burn on the hand