Finger Extensor Tendon Injury

(Mallet Finger; Boutonniere Deformity)


Tendons are responsible for connecting muscles to bone. The extensor tendons are located on the back of the hand and fingers. They let you open your hand and straighten your fingers. An extensor tendon injury is a cut or tear to one of these tendons. When they are damaged, you can lose the ability to extend your hand and/or finger(s). Two common extensor injuries are:
  • Mallet finger—the tendon is affected at the last joint on the finger, usually from a jammed finger
  • Boutonniere Deformity—the tendon is affected at the middle joint, usually caused by an arthritis-like condition
Extensor Tendons of the Hand
extensor tendon
Copyright © Nucleus Medical Media, Inc.


Extensor tendon injuries may be caused by:
  • A cut or laceration to back of hand or fingers
  • Broken bones
  • A crush injury
  • An open wound or cut
  • Jamming a finger
  • Arthritis
  • Nerve compression

Risk Factors

Factors that may increase your chance of an extensor tendon injury include:
  • Participating in certain sports
    • Basketball
    • Football
  • Arthritis


Symptoms may include:
  • Inability to open hand or fingers
  • Pain
  • Numbness or weakness
  • Cut to back of the hand or fingers
  • Jammed finger


You will be asked about your symptoms and medical history. A physical exam will be done. During the exam, you will be asked to bend and straighten your fingers. Your doctor will also check your fingers for sensation, blood flow, and strength. You may be referred to a hand surgeon or an orthopedist—doctor who specializes in bones. Images may be taken of your hand. This can be done with x-ray.

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