Finger Extensor Tendon Injury

(Mallet Finger; Boutonniere Deformity)


An extensor tendon injury is damage to the tissues on the back of the hand and fingers. It can make it hard for you to open your hand and straighten your fingers. The 2 types of this injury are:

  • Boutonniere deformity —harm to the middle joint of a finger, often from arthritis
  • Mallet finger —harm to the last joint of the finger, often from stretching it too far

Extensor Tendons of the Hand

extensor tendon
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Extensor tendon injuries may be caused by:

  • A cut to the hand or fingers
  • Stretching the tendon too far, such as when catching a baseball
  • A blow to the finger with an object, such as a ball
  • Weak tendons from health problems, such as rheumatoid arthritis

Risk Factors

This injury is more common in men and people who are middle-aged. Things that can raise the risk are:

  • Contact sports, such as:
    • Basketball
    • Football
  • Having health problems that weaken these tendons, such as rheumatoid arthritis


Symptoms may be:

  • A cut to the back of the hand or fingers
  • Pain and swelling
  • Problems opening the hand or fingers
  • A change in the way the finger looks or feels


The doctor will ask about your symptoms and health history. A physical exam will be done. The doctor will ask how the injury happened. The finger and hand will be checked. A doctor who treats bones or hands may be needed.


A splint will be needed to protect the finger as it heals. Other options are:


Medicine may be given to ease pain. Antibiotics may be used to treat an infection.


Some people may need surgery to repair the tendon. Exercises will also be given to help with finger strength and motion.


This injury happens due to accidents. There are no guidelines to prevent it.


American Society for Surgery of the Hand
Ortho Info—American Academy of Orthopaedic Surgeons


Canadian Orthopaedic Association
Trauma Association of Canada


Extensor tendon injuries. American Society for Surgery of the Hand website. Available at:
...(Click grey area to select URL)
Published 2014. Accessed September 23, 2019.
Leggit JC, Meko CJ. Acute finger injuries: part I. Tendons and ligaments. Am Fam Physician. 2006 Mar 1;73(5):810-816.
Mallet finger. EBSCO DynaMed website. Available at: Updated June 5, 2017. Accessed September 23, 2019.
Last reviewed September 2019 by EBSCO Medical Review Board Teresa Briedwell, PT, DPT, OCS, CSCS
Last Updated: 7/14/2020

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