Finger Extensor Tendon Injury
(Mallet Finger; Boutonniere Deformity)
Tendons are responsible for connecting muscles to bone. The fingers have tendons that run from the forearm through the finger. 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:
Extensor tendon injuries may be caused by:
Factors that may increase your chance of an extensor tendon injury include:
Symptoms may include:
Your doctor will ask 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.
Talk with your doctor about the best plan for you. Depending on the type of injury, you may require surgery. Surgery may be scheduled right away or within several days.
Treatment options include the following:
Depending upon the type of injury, you may receive antibiotics to prevent infection.
Tendons that are cut or ruptured require surgery. The hand surgeon may sew the tendon back together. A pin may need to be inserted through the bone to form a type of inside splint.
After surgery, you will be given a splint to protect your hand. Your doctor will tell you how long to wear it. It may be up to two months.
A physical therapist or occupational therapist will work with you for several weeks to regain your strength and range of motion. Right after surgery, movement will be limited. This will allow your hand to heal.
Some extensor tendon injuries are treated with a hand splint. Splints are worn until healing has occurred. This is usually several weeks.
Extensor tendon injuries are typically caused by accidental injuries. There are no known prevention guidelines for this injury. But, the deformities caused by these injuries may be prevented by taking certain measures, like splinting the finger or undergoing surgery.
of Orthopaedic Surgeons
American Society for Surgery of the Hand
The Canadian Orthopaedic Association
Canadian Orthopaedic Foundation
Extensor tendon injuries. American Society for Surgery of the Hand website. Available at:
Leggit JC, Meko CJ. Acute Finger Injuries: Part I. Tendons and Ligaments. Am Fam Physician. 2006 Mar 1;73(5):810-816. Available at:
To P, Watson JT. Boutonniere deformity. J Hand Surg Am. 2011;36(1):139-142.
Zhang X, Yang L, et al. Treatment of bony boutonniere deformity with a loop wire. J Hand Surg Am. 2011;36(6):1080-1085.
Last reviewed September 2013 by Teresa Briedwell, DPT, OCS