Boutonnière deformity: the middle joint that won't straighten, the splint, and exercises
A boutonnière deformity is a finger that bends at the middle joint and won't straighten, while the end joint bends back. After an injury it means the central slip, the tendon that straightens the middle joint, has torn, from a blow that forces the joint to bend, a dislocation or a cut. It can look like a sprain for days or weeks before the bent posture shows.
If the middle joint won't straighten on its own after a knock, get it checked within a few days: splinting works best early. The usual treatment is a splint that holds the middle joint straight for about 6 weeks while the tip keeps bending. This guide covers the signs, the splint, what to do if it's weeks old, and the exercises in and after the splint, with 3D demos.
Exercise is for pain that has been checked or is clearly mild and settling.
Get urgent medical help if
Call 999 or go to A&E after an injury (don't drive yourself) if your hand or a finger is numb, tingling or has pins and needles; a bone is sticking out or a bad cut is bleeding heavily; or a finger has turned blue, grey, white or cold.
Go to an urgent treatment centre or A&E if a finger looks out of shape, is crooked at a joint or is pointing at an odd angle, or you heard a crack or snap when you hurt it: it may be broken or dislocated. Don't pull on it or try to put it back. Support it in the most comfortable position, raise the hand, take off any rings, and don't drive yourself.
A cut on the back of a finger joint, even a small one: get it seen the same day, and go to A&E if you can't straighten the finger or have lost feeling. The tendon there lies just under the skin, and a cut can reach the joint.
Same day (NHS 111): the finger is the right shape, but you can't move or bend it properly or hold things; it's painful, swollen and bruised; the pain is severe or makes you feel faint, dizzy or sick; or you have a very high temperature or feel hot or cold and shivery. You'll probably need an X-ray, and NHS 111 will tell you where to go. If the finger is out of shape, go straight to an urgent treatment centre or A&E instead.
In the splint: swelling makes it tight or more painful, or the finger tingles, goes numb or changes colour. Contact your hand therapy team the same day, or NHS 111 out of hours.
After an operation or a cut: the wound is swollen, red and getting more painful or has pus coming out of it, or you also feel generally unwell or have a high temperature. Ask for an urgent GP appointment or get help from NHS 111.
See a doctor or physiotherapist if
Within a few days (NHS 111, a minor injuries unit or an urgent treatment centre): after a knock or a dislocation, the middle joint of a finger won't straighten on its own. It can look like a sprain at first, and splinting works best early.
In the splint: sore skin, a splint that has become loose, or a finger that has started to sit bent in the splint instead of straight. Contact your hand therapist promptly.
After the splint comes off, the finger droops again or doesn't straighten after your exercises: stop the exercises and contact your therapist.
An injury that is weeks or months old with a bent middle joint: still ask your GP for a hand therapy or hand surgery referral. Splinting is usually still tried under about 8 weeks, and casts or special splints can help some older ones.
A finger slowly bending into this shape without an injury, or swollen, stiff joints in several fingers: see a GP. The same posture can come from rheumatoid arthritis, which is treated differently.
After an injury or operation, pain that is getting worse instead of better or far worse than you'd expect, with swelling, colour or temperature changes, or skin that is very sensitive to touch: contact the clinic that treated you, your hand therapist or your GP promptly. It can be complex regional pain syndrome (CRPS), and early treatment may help.
You have diabetes and a hand problem: the NHS says hand problems can be more serious if you have diabetes.
Understand it
What it is
The tendon on the back of the finger splits into a central band, the central slip, which straightens the middle joint, and two side bands, which run on to straighten the end joint. If the central slip tears, the middle joint can no longer straighten and drops into a bent position. The straightening force shifts to the side bands, which slip towards the palm, pull the end joint back and make it hard to bend the tip.
That combination, the middle joint bent and the end joint bent back, is the boutonnière posture. Boutonnière is French for buttonhole: the joint pushes up through the gap between the bands like a button through a buttonhole.
A stubbing injury or a blow that forces a straight middle joint to bend, such as a ball on the end or back of the finger or a fall onto the back of the fingers; a dislocation of the middle joint, especially towards the palm; or a cut on the back of the joint. Sports reviews name basketball (a finger jammed while dribbling), volleyball (setting), baseball and American football.
In 15 people with a middle joint dislocated towards the palm, all had the tendon on the back of the joint torn, the seriousness was at first unrecognised, and it took more than 11 weeks on average to reach a specialist.
Pain and swelling over the back of the middle joint, a middle joint you can't straighten on its own, and an end joint that won't bend fully. The British Society for Surgery of the Hand (BSSH) says it can be hard to tell from the much more common middle joint sprains, as both cause pain, swelling and stiffness, and the bent posture may not appear for days or weeks. One NHS hand service says people tend to think the finger is just staved and often wait weeks before seeking advice. Early on, the side bands can still straighten the joint, which can mislead an examiner.
Clinicians use the Elson test: with the finger bent to a right angle at the middle joint over the edge of a table, you try to straighten that joint against their finger. With a torn central slip there's no straightening force, and the end joint goes rigid. In a study on donated fingers, it was the only one of four tests that reliably picked up the injury.
An X-ray looks for a piece of bone pulled off the back of the middle bone and checks the joint is in place; occasionally an ultrasound scan is used.
Untreated, the imbalance gets worse: the middle joint stiffens bent and the end joint bent back, sometimes within 2 to 3 weeks of the injury. One NHS hand service says injuries under about 8 weeks old are usually still splinted, though healing may take about 3 months. Older ones may not respond to splinting, and the finger's position is often best accepted, with surgery offered for a major loss of function.
The same posture can develop slowly, without an injury, in rheumatoid arthritis, from long-standing inflammation of the middle joint, and in osteoarthritis. The MSD Manual says it most often results from rheumatoid arthritis; in hand injury clinics, the usual cause is a stubbing injury. In a study of 111 fingers treated without surgery, deformities from inflammatory arthritis responded less well than injuries. Our hand arthritis guide and our rheumatoid arthritis exercise guide cover that.
The splint: consistent UK practice, but no trialsEmerging evidence
For a closed injury, every source we found uses a splint that holds the middle joint straight full time while the end joint keeps bending: for 4 to 8 weeks (the BSSH), 6 weeks full time and then weaning from 8 weeks (Hull), around 6 to 10 weeks (Gloucestershire), 6 weeks (the MSD Manual), or 6 weeks followed by 3 to 6 weeks of night splinting (sports reviews). Using the splint correctly matters, which is why a hand therapist usually checks it.
The BSSH says most injuries treated with a splint heal with satisfactory function, though it can take several months, and some fingers are left with a little loss of straightening at the middle joint or of bending at the end joint.
Splint or surgery: no trial has compared themMixed evidence
A 2019 systematic review screened 3,785 studies and found no randomised trials and no study comparing surgery with splinting; where rehabilitation was studied, it was always after surgery. A 2025 review agrees there are no trials comparing the two. So the choice rests on practice: a splint for a closed injury, and surgery for a cut tendon (UK standards ask for cut tendons to be repaired within days), a displaced piece of bone, a joint that has slipped towards the palm, or a finger that hasn't healed with splinting.
Starting early helps most: one studyEmerging evidence
In a US study of 111 fingers (106 people, 87% after an injury) treated without surgery, with splints, hand therapy and home exercises for about 15 weeks on average, the fingers graded poor fell from 63 to 28 and those graded excellent rose from 19 to 49. Fingers that started treatment within 6 weeks of the injury improved most, but no particular type or length of treatment did better; 7 got worse, and the authors note the deformity can persist. It looked back at records, so it shows an association, not proof.
Older injuries: casts and relative motion splints, in small seriesEmerging evidence
For a deformity weeks or months old, hand therapists may straighten the joint gradually with a series of casts, then use a relative motion splint, which holds the injured finger's knuckle a little more bent than its neighbours so the hand can be used. In one series, 15 long-standing deformities were cast straight and then splinted for 3 months, and all kept their straightening and could make a fist. In 28 people with long-standing deformities that could still be straightened by hand, tip bending improved from 47 to 67 degrees and the middle joint's lack of straightening from 22.5 to 12 degrees.
These are small series without comparison groups, and a 2026 review says more research is needed before relying on these splints for boutonnière.
In the splint the rule is straight, not painEmerging evidence
In the full-time splint, the middle joint must stay straight all day and night: don't take the splint off unless your therapist has shown you how. Letting it bend in these weeks can damage the healing tendon, and one NHS leaflet says the splinting then has to start again from the beginning. Bending the tip in the splint feels stiff at first; don't force it.
When bending starts, bend gently and only as far as your therapist sets: one NHS leaflet says a full fist with no strain or pain, and another says don't force the finger to bend. If the finger stops straightening after your exercises, stop and contact your therapist.
After the splint, a rule from an NHS wrist fracture booklet fits grip and strength work, borrowed: an effort of up to about 5 out of 10 that settles within 30 minutes. No heavy lifting or contact sport until about 12 weeks.
Start at the first stage. Each move opens a full guide with a 3D demo.
Stage 1
The splint: middle joint straight, tip bending (about weeks 0 to 6, as your team allows)
As your team allows, from the day the splint is fitted. The middle joint must stay straight all the time: don't take the splint off unless your therapist has shown you how. Keep it dry and away from heat. Bend the end joint in the splint, holding the splint with your other hand (steps below). Keep the hand raised, and keep the other fingers, thumb, wrist, elbow and shoulder moving. Light use with the splint on; no heavy gripping or lifting.
Tabletop only: bend the big knuckles with the fingers straight, 5 times with 5 s holds, every 1 to 2 hours, splint on · Leave out the hook, full fist and straight fist, which bend the middle joint. NHS leaflets' dose
5 breaths, the out-breath longer than the in-breath, a few times a day · The move page's dose; how often is our suggestion. It lifts the hand above your heart
Move on when: Your hand therapist checks the finger, usually at about 6 weeks, and it stays straight on its own.
Follow along: a timer, a cue and the next move, one step at a time.
Stage 2
Weaning: the middle joint starts to bend (about weeks 6 to 8, as your team allows)
As your therapist sets. Out of the splint for exercises only, and back in it between exercises and at night; some services start earlier, from about 3 to 6 weeks, with an exercise splint that lets the joint bend a set amount, increased each week. Bend gently, with no strain or pain. Single-joint bends of the middle joint go only to the angle your therapist sets (steps below). If the finger stops straightening after your exercises, stop and contact your therapist.
A gentle full fist first, then the hook and straight fist when your therapist adds them: 5 times with 5 s holds, every 1 to 2 hours · An NHS leaflet's order and dose (a gentle full fist from weeks 5 to 6, the hook and straight fist from week 7)
Move on when: The finger straightens fully on its own after your exercises, and your therapist starts weaning you off the splint, often from about 8 weeks.
Follow along: a timer, a cue and the next move, one step at a time.
Stage 3
Grip and full use (from about 8 to 12 weeks, as your team allows)
As your team allows. Wean off the splint as your therapist says, and build grip gradually. Contact sport and heavy lifting usually wait until about 12 weeks, and getting full use back can take several months. The doses are editorial.
Move on when: Your grip is close to the other hand's and the finger stays straight. The grip strength workout takes it from here.
Follow along: a timer, a cue and the next move, one step at a time.
What to change for now
Bending the tip in the splint (written steps)
Our 3D figure can't show this. It keeps the tip from stiffening and may help keep the side bands in place. It's the end-joint part of the finger joint blocking move, with the splint doing the holding.
1. Keep the splint on, and rest your forearm on a table.
2. With your other hand, hold the splint firmly between your thumb and fingers, so the middle joint can't bend.
3. Bend the tip joint as far as it goes, hold for 3 to 5 seconds, then straighten it.
4. Do this 5 times, every 1 to 2 hours, or as your therapist sets.
5. Also bend the big knuckles with the fingers straight (the tabletop), holding for 5 seconds.
Bending the middle joint, when your therapist says (written steps)
Only when your therapist starts it: usually with an exercise splint that limits the bend, increased each week, or out of the splint at about 6 to 8 weeks.
1. Sit with your forearm on a table, palm up.
2. Hold the finger just below its middle joint with your other hand, so the big knuckle stays straight.
3. Bend the middle joint gently, only as far as your therapist has set, then straighten it fully.
4. Check it straightens fully after each set. If it doesn't, stop and contact your therapist.
For a deformity that is weeks or months old, a hand therapist may use a series of casts to straighten the joint, then a relative motion splint for about 3 months; this rests on small case series. Don't try to force it straight yourself.
A finger that bends at the middle joint and won't straighten, while the end joint bends back. After an injury it happens when the central slip, the tendon that straightens the middle joint, is torn.
What causes it?
Usually a stubbing injury or a blow that forces the middle joint to bend, a dislocation of that joint, or a cut on the back of it. In arthritis it can develop slowly without an injury.
How can I tell it from a sprain?
Early on it's hard: both cause a swollen, painful middle joint, and the bent posture can take days or weeks to appear. A clinician can test the tendon with the Elson test.
Is it urgent?
If the middle joint won't straighten on its own after a knock, get it checked within a few days. Splinting works best early, and the joint can stiffen bent within weeks.
How long do I wear the splint?
Usually about 6 weeks full time, between 4 and 8 depending on the injury, then weaning or night wear. Contact sport and heavy lifting usually wait about 12 weeks.
Can I take the splint off?
Not unless your therapist shows you how. Bending the middle joint during the full-time weeks can damage the healing tendon, and the splinting may have to start again.
What exercises should I do?
In the splint, bend the end joint while holding the splint, and bend the big knuckles with the fingers straight. Bending the middle joint starts only when your therapist says.
Will I need surgery?
Usually not for a closed injury. Surgery is for a cut tendon, a large displaced piece of bone, a joint that won't stay in place, or a finger that doesn't heal with splinting. No trial has compared splinting with surgery.
Is it too late to fix an old boutonnière?
Not necessarily: under about 8 weeks, splinting is still usually tried, though it may take about 3 months. Older ones may respond to casts and special splints, or be best accepted if the finger works well.
Will my finger be straight again?
Most splinted fingers end with satisfactory function, sometimes with a slight loss of straightening or bending. Getting full use back can take several months.
Is a boutonnière the same as a swan neck deformity?
No, they're opposites: in a swan neck, the middle joint bends back and the end joint bends down. A swan neck can follow an untreated mallet finger or a volar plate injury.
I have rheumatoid arthritis and my finger has bent. Is it the same thing?
The shape is the same, but it comes from long-standing joint inflammation and is managed differently, by your rheumatology and hand teams. In one study it responded less well to splinting than an injury did.
Exercise education, not a diagnosis or treatment plan. It is written from the guidelines and studies listed above; review by a clinician is pending. If your pain follows an injury, is severe, is getting worse, or comes with any warning sign listed on this page, get it assessed. Health disclaimer.
