Boutonniere Deformity
A finger bent down at the middle joint and up at the tip
Quick Facts
- Type: Finger tendon deformity
- Cause: Central slip tendon injury or arthritis
- Appearance: Middle joint bent down, fingertip bent back
- Treatment: Splinting; sometimes surgery
Overview
Boutonniere deformity is a characteristic bending of a finger in which the middle joint (the proximal interphalangeal, or PIP, joint) is bent downward and the fingertip joint (the distal interphalangeal, or DIP, joint) is bent backward. The name comes from the French word for buttonhole, because the bent joint can poke through the surrounding tendon tissue much like a button through a buttonhole.
The deformity develops when the part of the extensor tendon that straightens the middle joint, called the central slip, is torn or weakened. Without this support, the middle joint droops and the side bands of the tendon slip down, pulling the fingertip into an upward position. Boutonniere deformity can follow a finger injury or develop gradually in inflammatory conditions such as rheumatoid arthritis. Early treatment, usually with splinting, gives the best chance of restoring a straight, functional finger; once the deformity becomes fixed it is harder to correct.
Symptoms
The signs of boutonniere deformity may appear within hours of an injury or develop more slowly over days to weeks.
- The middle joint of the finger cannot be straightened and bends downward
- The fingertip joint bends backward and may be hard to bend down
- Swelling, pain, and tenderness over the middle joint, especially soon after injury
- Difficulty fully straightening or using the finger
- A finger that catches or looks crooked
After an injury, the deformity is sometimes not obvious right away and develops over the following one to three weeks, which is why a swollen, painful finger that cannot straighten should be evaluated promptly.
Causes
Boutonniere deformity results from loss of the central slip's support of the middle finger joint. Common causes include:
- Forceful bending: A blow that suddenly bends the straightened middle joint can rupture the central slip.
- Cuts and lacerations: A cut over the top of the middle joint can sever the tendon.
- Jamming injuries: Sports injuries that jam the finger can damage the tendon.
- Rheumatoid arthritis: Long-standing inflammation can erode and weaken the central slip, producing the deformity gradually.
- Dislocation: A dislocation of the middle joint can tear the supporting tendon.
Risk Factors
- Participation in ball and contact sports
- Rheumatoid arthritis or other inflammatory joint disease
- Cuts or crush injuries to the top of the finger
- Previous finger dislocation or jamming injury
- Work or activities with a high risk of finger trauma
Diagnosis
A clinician usually recognizes boutonniere deformity from the position of the finger and a focused examination.
- Physical examination: Testing the ability to straighten the middle joint against resistance, which is weak or lost when the central slip is torn.
- History: Asking about a recent injury or a background of arthritis.
- X-rays: Looking for a fracture or a bone fragment pulled off by the tendon and assessing arthritis-related joint changes.
Because the full deformity can take time to appear, a doctor may recheck a swollen, recently injured finger over the following weeks.
Treatment
Most boutonniere deformities, especially when treated early, respond to nonsurgical care that holds the middle joint straight while allowing the tip to move.
- Splinting: A splint keeps the middle joint fully straight, often continuously for around six weeks, to let the central slip heal in the right position.
- Hand therapy: Exercises to bend the fingertip while the splint is on, and later to restore motion and strength, help prevent stiffness.
- Treating the cause: In rheumatoid arthritis, controlling the underlying inflammation is important.
- Surgery: Considered for cut tendons, deformities that do not improve with splinting, or fixed deformities, to repair or rebalance the tendon.
Sticking closely to the splinting schedule is essential, because removing the splint too soon can allow the deformity to return.
Prevention
- Seek prompt evaluation of any finger injury that limits straightening
- Use protective taping or guards in sports that risk finger jamming
- Treat finger cuts over the joints promptly
- Manage rheumatoid arthritis and other inflammatory conditions with your care team
- Follow splinting instructions fully after a central slip injury
When to See a Doctor
See a doctor promptly if you cannot straighten the middle joint of a finger after an injury, if a finger is swollen and painful over the middle joint, or if you have a cut over the top of a finger joint. Early splinting offers the best chance of a good outcome, while a deformity that becomes fixed is harder to correct. Seek urgent care for a deep wound over the joint, signs of infection such as spreading redness or pus, or a finger that looks dislocated.
Frequently Asked Questions
What causes boutonniere deformity?
It is caused by injury or weakening of the central slip, the part of the extensor tendon that straightens the middle finger joint. This can happen from a forceful blow, a cut, a jamming sports injury, a dislocation, or gradual damage from rheumatoid arthritis.
Can boutonniere deformity be fixed without surgery?
Often yes, especially when treated early. Wearing a splint that holds the middle joint straight for about six weeks allows the tendon to heal. Surgery is usually reserved for cut tendons, deformities that fail splinting, or fixed deformities.
How long do I need to wear the splint?
Splinting typically continues for around six weeks of holding the middle joint fully straight, sometimes followed by part-time use. Following the schedule exactly matters, because taking the splint off too early can allow the deformity to come back.
What is the difference between boutonniere and swan neck deformity?
In boutonniere deformity the middle joint bends down and the tip bends up. In swan neck deformity it is the opposite: the middle joint hyperextends (bends backward) and the fingertip bends down. Both can occur with finger injuries or rheumatoid arthritis.
Will my finger straighten normally again?
When treated early, many fingers regain good straightening and function. A deformity that has become fixed before treatment may not fully correct and can leave some lasting stiffness, which is why prompt evaluation and consistent splinting are important.
References
- American Society for Surgery of the Hand (ASSH). Boutonniere Deformity.
- American Academy of Orthopaedic Surgeons (AAOS). Finger injuries and deformities.
- MedlinePlus, U.S. National Library of Medicine. Finger injuries and disorders.
- OrthoInfo, American Academy of Orthopaedic Surgeons.