Radioulnar Synostosis

Radioulnar synostosis literally means a bony union between the two forearm bones.  Normally, the ulna bone acts as a straight “post” to anchor the wrist to the elbow.  The radius bone rotates around the ulna to allow the forearm to turn palm up and palm down.  This rotation is helpful for daily activities and allows many actitivies such as typing on the keyboard (palm down or “pronation”) or hold change (palm up or “supination”).  Almost all rotation comes through the forearm (ie the relationship between radius and ulna) but some can come through the wrist bones also.

Some kids are born with a bony connection between the radius and ulna.  This bony “bridge” can also develop after a trauma in an adult.  When that happens, the bones are no longer separate and the ability to rotate the forearm is not present.  Because the shoulder is so mobile, we can make up for some loss of forearm rotation with shoulder movement.  It is pretty easy to pull arm away from body- abduct- and the hand assumes a palm down position.  It is less easy to move the shoulder in such a way to allow the palm up position.

The bottom line is that kids adapt amazingly well to radioulnar synostosis.  Often, families do not even realize this condition is present until after kids start school.  There is no pain and, as noted above, some rotation can be achieved through the wrist.  When both sides are affected, it may be a little more challenging to adapt.  Additionally, it matters in which position the forearm is fused.  The forearm can be “stuck” in full palm up (supination), full palm down (pronation), or anywhere in between.  The best position is half- way between (the clapping position) which allows the patient to use the shoulder to help accommodate in both directions.  Palm down is better than palm up as so many of life’s activities are palm down (keyboarding, etc).

In a small number of kids, the forearm position causes trouble with activities.  In those, a small surgery can be done to reposition the forearm in a better position for function.  The pictures below show a patient positioned with both forearm in mid rotation.  He has no issues with function despite his limited rotation.

Synostosis with full elbow extension
Synostosis with full elbow flexion
Synostosis with attempted supination- palm up

Synostosis with attempted pronation- palm down

Xray showing synostosis near elbow.  The two bones are joined together.


  1. Hi I'm 27, Recently underwent derotational osteotomy for RUS,my doctor kept it in almost supination position, before surgery my hand is in semipronaed position,it was very good position,but now I am feeling very disappointed, with this position I can't drive or type keyboard,my question is that,can I go for another surgery for neutral position,is it recommended now?

  2. Asif,
    Thank you for the question. I am uncertain how to answer your question. If the position is making your function more difficult, then it would be reasonable to consider another surgery. The supinated position is, in my experience, difficult for function as you mention. Good luck.

  3. I have radioulnar synostosis. I'm 28 and 6'4. I wanted to add with the others that life with this "disability" is not that bad. There are certainly times where I am self conscious about how it looks and that effects a lot of what I do and what I wear, but I do not, AT ALL, consider myself less competant than others. Usually most people don't even notice or at least don't care. I still have been able to date attractive girls, make friends, whatever. I would like to change it but I can deal with it if I can't. Don't worry too much about it, embrace your differences.

  4. Hi! Happy to have found this thread. Born with RUS in my left arm only. Mom put me in baton as a child to help me learn to live with it. I'm 31 now and starting to experience elbow and shoulder pain. Not sure what kind of doctor to see since I'm not really a surgery candidate. Is an orthopedic surgeon the only one or are there others?

    How are people treating the pain?

    Would also love to know how others are building muscle. I love weights and it's a challenge to build upper body strength, evenly. There's a short thread about this on, but no answers yet. Would love to find a fitness trainer with this!

  5. ABn3d,
    Thank you for the comment and question. Pain is uncommon. Strengthening may help to a degree but therapy to correct (as possible) your mechanics probably will help. You are undoubtedly compensating for the lack of forearm rotation and perhaps selective strengthening with a therapist will help. A physiatrist is another type of expert who could help. Good luck.

  6. Hello Eppie- thank you for the question. Surgery for radioulnar synostosis is usually not required but may be helpful for function in certain situations (such as when both arms are affected or if the forearms are stuck in severe palm down or palm up position). If your daughter is functioning well at age 10, she probably would not benefit from surgery.

  7. I’m in my 60s. Fortunately, only my right arm has synostosis in full pronation. I come from a long line of left-handers and I myself am a lefty. So, my limitations have been few. I couldn’t play baseball well due to the condition, making me the butt of ostracism as a boy. I cannot lift a bulky heavy object with ease, so I’ve learned to take more with my normal arm. Otherwise, small tasks requiring manipulation cause me to work around them using my good hand. I worked on construction in summers as a student with little problem. Most people don’t notice my condition, but some do and can be quite insensitive. I put off truly insensitive people with the retort: “It’s a war injury,” which shuts them up immediately. Years ago, I met a fellow with the same condition (bilaterally). Our handshake was, to say the least, awkward.

    My parents took me to an orthopedic surgeon when I was four, and again at 18. The surgeon said there was no good option surgically. And he said he felt I functioned very well. My pediatrician always urged me to exercise that arm with weights, which I’ve always done.

    I have two daughters, neither having inherited the condition.

    So, I’ve managed to get through life just fine. But, oddly, I can’t say that I’ve always been used to it. I’m constantly cognizant of the deformity, its visibility and the physical limitations that come with it. Had there been a reliable fix, I would have jumped at it. But I also view myself as lucky – being unilateral and with no other associated conditions.

  8. James,
    Thank you for sharing your experiences. My patients have shared similar feelings and we typically offer surgery to reposition the forearm in less of a palm down position (ie, more neutral). Nonetheless, even in full pronation, as you so nicely share, function tends to be very good, if not occasionally awkward.

  9. interestingly I have a identical twin brother who is completely fine. we were premature twins so the debate was the doctors messed me up and that it wasn't a disorder(because apparently I was still developing)as my twin brother wasn't ready to go out and i pushed my way through.Another theory was he slept on my arm in the womb(yeah we were in the same one)apparently its the fact they have pictures where he is on top of me.. Do you think that is true?or was i naturally destined to have it.

  10. I'm 21 years old and I was born with this disorder in my left hand my right hand is completely normal,my family and I didn't find out about this until i was much older like 13 maybe, I was trying to play the guitar and couldn't we went and got x rays and found out my radius and ulna are fused at the elbow joint. I think its palm down and there is completely 0 rotation,but I'm an athlete i have played most sports from cricket,basketball(a bit hard but possible),baseball but I mostly play soccer no trouble with that. the only annoying thing is when it comes to like events serving myself food is a bit hard.and also its kinda smaller than my right hand so it just looks wrong so i'm usually just always in long sleeves.

  11. Thank you for your comments. Helpful to hear how functional you were and are. It is common that only one sibling is affected as in most patients, this is a sporadic finding rather than a genetic one. This is caused by a failure of separation of the radius and ulna during the developmental process. I do not think it has anything to do with his position in the womb. Good luck!

  12. Hi there, I have had 'limited supination' in both arms — 90 degree rotation– in both arms, my entire life and at 57, have just started experiencing shoulder pain that I attribute to overuse compensating for my lack of elbow rotation. I overextend the shoulder to get my right hand into the palm up position. Any remedies for this? (Other than avoidance activity?)

  13. Holmgren,
    Thank you for writing. We know that the outstanding mobility of the shoulders does help to minimize the functional limitations of the fused radius and ulna. This is 'easy' for trying to get the hands in the palm down position (pronation) but harder to achieve palm up (supination). We (people like me) worry about what happens over time but you are the first who has shared this pain. While avoidance is an option, there may be therapy that can help strengthen the shoulder muscles which might help. A good shoulder surgeon may also have options (even one who does not know much about the forearm). Good luck and let us know what happens.

  14. Hi , I've had RUS all m y life. I was a pretty good volleyball player despite not having good supination in either arm….about 45* I have always wanted to play the guitar, but can't get my left arm around the neck of the guitar. Is it reasonable to consider surgery to pursue this???

  15. Thank you for the question. While I would be pleased for you to find a way to play the guitar, I do not think that surgery likely makes sense. My reasoning is that to gain supination, you will lose pronation. That may be too high a cost. There may be modifications to allow you to play- a good occupational therapist may have ideas. Good luck.

  16. Hello. I was born with RUS in both arms. My left arm cannot turn supine past 90 and my right can only turn a bit past 90. So basically not at all. I was diagnosed on 9/11/01 when I was 13. I have noticed that the muscles in my forearms are noticeably smaller. Turning doorknobs requires me to dip my elbow. In fact My parents first noticed the condition when I was unable to open a door while carrying a paper grocery bag in my arms. Besides getting change in a drive through, bicep curls, fielding a ground ball, bowling, taking a football snap under center (very awkward) and other things like that, this issue hasn’t really affected me that much. I played college football for 4 years as a defensive back, where I could even hang clean 300lbs with a slightly awkward arm / wrist position. During my diagnosis I was told about and considered surgery. I am glad that I did not. At 30 I can say that I have lived a perfectly normal life. I can only hope I don’t experience pain in the future. In fact I am a jiu jitsu practitioner and have found that utilizing my “boney forearms” is very useful against my opponents. Have never met or talked to anyone else with it. Only began researching it lately. Hope this might help people with young kids.

  17. Braden,
    Thank you for the comment. Your perspective will be very helpful for families to read. I will add that, unfortunately, for some kids, the position of the RUS will interfere with activities more than you have experienced.

  18. Very glad to have come across this page. I'm 43 and always wanted to know why I can't drop or turn my left wrist and face the palm upwards. It gets stuck facing right when I turn from palm down to palm up. Realised this at age 10 when my karate teacher tried to manipulate my hand to a position I physically couldn't do. Also means I'm stuck at a basic level of guitar. Barre positions are impossible. Sounds like there are much more serious implications for some folks out there so guess I'm lucky. Again thanks for this page, I now have a name for my funny arm as mum calls it.

  19. Hello, I am a ballet dancer with Congenital Radioulnar Synopsis. Many aspects of ballet require the rotation of the forearm. I'm not sure if there are physio therapy exercises for resolving the issue??

  20. Hi everyone,

    I'm 34 year old male and live in Perth, Western Australia. I have bilateral radioulnar syntosis in the pronated position.

    I am a super active person and have tried almost every sport there is – golf, squash, tennis, snooker, hockey, shooting, ping pong, soccer, jiujitsu, boxing – just to name a few! The only 'problem' encountered is collecting change! I barely even think about not being 'normal'. Any way, even though knowing that surgery may have been an option, it was never an option that I wanted to take – I've found a way to do everything I wanted.

    I'm now at a stage in my life where my wife and I are pregnant with our first child – and so for the first time in my life I have begun to research the condition just to get an indication on whether my child would inherit the condition. Based on my reading there will be a 50% chance it will be passed down. If it is passed down I just hope it is no worse than my condition.

    There's no clear sign of this running in my family, although my grandfather may have a minor case of it but he seems to have rotation in both arms, which makes me wonder if mine is hereditary (baed on my grandfather's slight issue, I I'm guessing that it is).

    Like many here, I thought this condition was so rare and thought I was an outlier, I never expected to see so many people with the same experiences and similarities as myself. To be honest, it makes me feel less alone about it – and that if my child has what I have they'll be alright. I've never posted a comment or a blog in my life so I guess it shows that I'm a little concerned about what may happen 9 or so months down the line. If anyone has any advice or information to share on this, that would be much appreciated.

    Growing up, I would have loved to have spoken with someone who had the same thing; for advice or just to talk about how to feel about things. If anyone who's reading this wants to reach out, I'm here if you want to chat.

    Thanks for the forum, Dr Goldfarb.

  21. Ads,

    Thank you for writing. I look forward to any comments from the group. My only addition would be that the position of the synostosis matters (stuck in neutral vs palm up vs palm down) for function. So the fact that you are able to be so active is wonderful but not everyone with every position of their synostosis could like accomplish the same.

    I would also add that while this can be an autosomal dominant condition with a 50% chance of being passed on to your child (congrats), it can also be sporadic with a less predictable pattern of inheritance.

  22. I would suggest looking into unilateral training for most upper body compound movements like bench press, shoulder press, rows as you won't have the same movement on each. Maybe avoid the dumbbell curls as you'll be building strength from the compounds. Having said that, I'm bilaterally pronated, I weigh about 68kg but can easily curl 30kg per arm – all palm facing down – so there's no reason why you can't do dumbbell work on curls. In terms of shoulder pain, I've got some on my right side, and that it because my chest and shoulders work overtime – especially from weight training. But I'm also attributing that pain to being lazy on stretching, yoga etc so I'm now focusing on getting the weaker surrounding muscles stronger. Physiotherapy works – only if you do the work consistently. Good luck with training – it's a challenge sometimes but you always find a workaround. Actually, another good idea would be build grip strength on your left – that helps a bunch around building the forearm up around the elbow.

  23. Hello. We are from Russia. Our child (7 months old) has radial synostosis from birth (left arm, pronation, palm down, with dislocation of the radial head). At present, we conduct long-term (20 sessions) massage courses with ozokerite + paraffin + in parallel treatment with a chiropractor (orthopedic surgeon). These 2 specialists say that it’s realistically to separate the bones and “adjust” the radius bone “into place” and intend to do this. Do you think it's possible to do this? .. Faced with this in practice? Please comment.

  24. Thank you for the question. The literature is pretty clear that trying to put the radial head in place and separate the joined bones is rarely successful. That is also our experience over many years and I would not attempt this surgery any longer. There are so many forces acting on these bones that it just does not seem reasonable to expect that it would be successful.

  25. I am 33, and may have Kleinefelter syndrome. I was looking at some information that includes this syndrome. I don't know if I have it, and if I do, I have a pretty good range of motion – palm down is easy, middle is easy, but to achieve palm-up I absolutely have to use my shoulder. Otherwise, I am not able to rotate the last 60 degrees or so to fully palm-up.
    I first noticed this when playing baseball, when I favored turning my hand "backwards" (more pronated) from other children and avoiding palm-up positions to catch balls.

    Could you please point me to the right kind of doctor to check this?

  26. I am 44 and all my life I have never been able to turn my palms flat upward when my arm is bent. For example if getting change at stores, it would just fall, or if doing yoga I can’t turn palms upward on my knees. I always thought my wrists were messed up! Turns out I have a slight fusion also. Not bad enough that I can’t turn my hand enough to live my life normally, but enough so that I drop things, when I walk carrying cups i cannot keep them upright and spill, etc. It took all my life to find out about my arm bones.

  27. Hey all.
    I have RUS in both arms. They are palm down in resting position and I can turn both 90 degrees. Being as im 35 years old I have adapted well. To those of you looking for ways to help your kiddos if they are young enough they havent adapted or are struggling and there's a Dr by all means do what you think is best. However ive never had any surgeries on mine. I didnt know it was an actual thing that happens sometimes until I was about 18. My mother asked her dr who asked a colleague of his that worked in new york that had seen a case like mine. But as far as limitations there are few. Collecting change is awkward and people dont know how to take it. The technique I use is to form a cup with my fingers for them to drop the change in or use the cash to make a funnel to get the change in my finger cup. Lol. Sounds funny when I'm explaining it. We as humans adapt and it may be a struggle for some but you will adapt I promise. Anyway. As I said I'm 35 and I have adapted well enough that I am a union welder/pipefitter, I have blown glass, I do wood working, I do clay pottery, I do tie dye, I'm always trying things to see if I can do them. If I feel like my RUS is going to limit me I figure out a way to overcome it. Also ive never had any pains or issues from mine. Anyway I feel like I'm rambling at this point. However to anyone that is struggling with this I would like you to know, you are not alone. There are lots of us with this situation, dont think of it as a disability or a deformity. It makes us unique, own it.

    Positive vibes to all.
    Thank you for your time.

  28. Jorden,
    Thank you for your comments and tips. Really great wisdom for all! It is uncommon to be able to turn the forearm part- way but it does happen. More commonly, we compensate through extra wrist motion.

  29. This is a very late reply but I have been trying to find the name of the problem I have.
    I have this in my left arm, palm down. I an no 41 and have dealt with this my whole life. As it a normal thing for me, I forget that it is a disability, until I try and do normal things, like carry a box, eat fine dining, or simply giving someone a hug. As a kid it affected me more since I was unable to learn to play any of the string instruments. I do worry that, if I ever break my right arm, I will be incapacitated. Simply using a spoom with my left hand is a balancing act, with anelboy sticking out at an odd angle. I can position my hand and arm in the illusion that I have 90deg movement, but the reality is, my whole body will shift slighty. Its second nature.
    I advise anyone who doesnt find it a complete disruption to life, not worry about it. You apapt and its normal.

  30. I am 36 and I have never been able to turn my left hand to palm up position, it never has been able to turn. My mother thinks it was broken during delivery of my birth. Wonder what could be the issue there and is it something that can be fixed. I wouldn't care about breaking it and being in a cast for a few months that's fine, as long as it's able to turn how a normal hand does. Any suggestions?

  31. Erick,
    Thank you for the question. Most likely this is birth difference rather than a result of fracture (but obviously, I do not know that for certain). As noted on the blog, we can reposition the forearm into a different position but we cannot reliably restore motion. An xray would be very helpful.

  32. Dr Goldfarb, I’d would like to extend a hearty thanks for addressing questions and comments on this post. You provide great feedback- and encouragement – to those with RUS. It’s frustrating to suffer from it but good to know there’s someone out there who recognizes the issues. Thanks.

  33. I am an OT and I am seeing a 4 year old for therapy. Big issue is not being able to wipe herself well. Any suggestions? She is little so using a toilet wand seems challenging. I recommended a bidet for home, but what about school?

  34. Hello. Thank you for writing. I agree this can be a challenge especially with a full pronated (palm down) position. Those are the patients that I believe can benefit from surgery. Else, your suggestions are how we think about this challenge as well. Sorry that I do not have additinoal suggestions.

  35. Hello
    my names Ryan and I'm 19 in about 2 weeks, I was born with RUS, I inherited it from my dad. I didn’t know much about this condition until I recently started doing research about it and I didn’t know there was other people that had it until I came across this page and read about their situations.
    I can’t turn my left hand with my palm facing up (Supination), I can only turn my palm facing down (Pronation) and to the right (Clapping position). It hasn’t really affected me growing up through school until I turned about 16 and started getting into fitness which is when I realised I couldn’t do bicep curls properly but I found ways around it like hammer curls and using the tricep rope as a pull up motion as its flexible making it easier to curl.
    I was training to join the army which turned out pointless as I didn’t pass my medical due to this condition, I was rejected from the army which really let me down.
    Since I couldn’t go down the military route I went into the construction route and trained to be a bricklayer but I still find it hard at times to do certain stuff like picking things up and using techniques with tools as I ain’t got that supination motion to hold bricks etc from the bottom with my left hand.
    It gets stressful at times but I try to deal with it, I know my condition ain’t as bad as others but it still affects my life and joining the military is what I’ve wanted to do since I was a kid as living a ‘normal’ life just doesn’t interest me.
    Is it possible for me to have surgery to be able to have full motion in my left hand if not more than I currently have and if so where can I go for surgery, I’m From the UK, Liverpool. I don’t mind travelling if it means I can get this done as it would really change my life. If you need to contact me via email it’s:
    Hope you get back in touch soon would really appreciate it.

  36. Ryan- thank you for writing. Unfortunately, restoring forearm rotation is simply not possible. Even if addressed at an early age, we, as surgeons, cannot reliably improve motion. Surgeries generally reposition the forearm but it sounds as though your forearm is in as a good a position as possible. Good luck.

  37. Hello, I'm 15 and only have RS in my left arm and can rotate my wrist into a clapping position. It has restricted movements like bicep curls, boxing uppercuts, chin ups… is it worth getting surgery or is the success rate too low?

  38. My daughter was born with this condition in both arms. She only has about 5 degrees rotation in both arms. Her arms are in pronation . I discovered it when she was around 2 years old and we have been back and forth to the doctor for her entire life. Unfortunately none of her doctors had very much experience in treating the condition and never considered surgery no matter how many times I asked them. They send her to PT she has been in casts, braces, had numerous x rays and MRI. She is now 17 and experiencing tremendous amounts of pain every day, she's beginning to have numbness and shooting pains and the doctors are still opting out of surgery. This condition has made her have to quit her job, miss school, and miss out on other things because its causing her so much pain. I have researched Boston childrens hospital but we live in NC and cant afford the travel. I feel so helpless, I trusted her doctors but now I just don't know. My question to you is, do you think it is too late for surgery?

  39. Hello. I am sorry for your daughter's challenge. As you know, we cannot reliably restore motion but there are, as noted here, ways to reposition the forearms. That really can be done at any age. I would not promise that such a surgery would solve all of the listed issue but I would hope it could be helpful. Good luck.

  40. If the dislocated radial head is painful, excision is a good option. I do prefer to wait until the bones are finished growing before excision. There are risks with the procedure related to bone/ joint stability. For most patients, radial head excision does quite well.

  41. I'm 71. My parents discovered my unilateral RUS (right arm) when I was around 5 and took me to an orthopedic surgeon. I went back to see him at 18. He wisely advised that I avoid surgery, but that if I wanted to go ahead with it, he described a procedure that was not simply repositioning and would've resulted in diminished strength. I declined. My arm is in the fully pronated position. It hindered in me in some sports, particularly baseball and my handwriting is terrible. Fortunately, I come from a long line of left-handers and am one myself. Though born with this condition, I've never felt comfortable with it. It does hinder me somewhat in some basic functions, but these are minor. All that said, I'm grateful that I wasn't born with bilateral RUS.

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