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Disease Profile

Congenital radioulnar synostosis

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.



US Estimated


Europe Estimated

Age of onset






Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

Radio-ulnar synostosis; Radioulnar synostosis; Radial-ulnar synostosis


Musculoskeletal Diseases


Congenital radioulnar synostosis is a rare condition in which there is an abnormal connection (synostosis) of the radius and ulna (bones in the forearm) at birth.[1] The condition is present in both arms (bilateral) in approximately 60% of cases.[2] Signs and symptoms depend on the severity of the abnormality and whether it is bilateral; people with the condition often have limited rotational movement of the forearm.[1][2] Pain is usually not present until the teenage years.[2] There are 2 types of radioulnar synostosis: type 1 and type 2. In type 1, the fusion involves 2-6 cm of the area between the radius and ulna bones which is closer to the elbow and the knobby end of the radius that meets the elbow is absent (radial head). In type 2, the fusion is farther from the elbow and there is dislocation of the radial head. Both types result in a limitation of inward roll (pronation) and outward roll (supination) of the forearm, and in type 2 there is also a restriction of extension at the elbow.[3] Congenital radioulnar synostosis is due to abnormal fetal development of the forearm bones, but the underlying cause is not always known. It is sometimes a feature of certain chromosome abnormalities or genetic syndromes.[1][2][3] Some cases appear to be inherited in an autosomal dominant manner.[3] Treatment may be conservative or involve surgery depending on the severity of the abnormality and the range of motion.[1]


This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
Percent of people who have these symptoms is not available through HPO
Autosomal dominant inheritance
Dislocated radial head
Limited elbow extension
Decreased elbow extension
Elbow limited extension
Limitation of elbow extension
Limited extension at elbows
Limited forearm extension
Restricted elbow extension

[ more ]

Radioulnar synostosis
Fused forearm bones


Congenital radioulnar synostosis is caused by abnormal development of the forearm bones during the fetal period, although the underlying cause of the developmental abnormality is not always known. The condition may be isolated (occur without other abnormalities) or it may be associated with various other skeletal, heart (cardiac), neurologic, or gastrointestinal abnormalities. When other abnormalities are present, the condition may be due to an underlying genetic cause, including a variety of syndromes or chromosome abnormalities.[2][3] Some chromosome abnormalities that may include radioulnar synostosis are Klinefelter syndrome and XXXY syndrome. Examples of genetic syndromes that may include radioulnar synostosis are Apert syndrome, Crouzon syndromeCarpenter syndromearthrogryposisTreacher Collins syndromeWilliams syndrome, amegakaryocytic thrombocytopeniaand Holt-Oram syndrome.[2][3][4]


Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.

Testing Resources

  • Orphanet lists international laboratories offering diagnostic testing for this condition.


    Congenital radioulnar synostosis may be treated with surgery. Surgery is more commonly performed in patients who have bilateral radioulnar synostosis and/or patients who have very limited movement due to the radioulnar synostosis. In some cases, surgery is best performed in early childhood, usually before school starts, and in some cases it may need to be done in several stages. Surgery is not generally recommended for older patients with milder deformities who have learned to compensate for the limited range of movement caused by the synostosis, by using their shoulders and/or wrists. Complications of the surgery may include nerve damage or recurrence of the fusion.[2] 

    For in-depth information about the treatment of congenital radioulnar synostosis, please visit Medscape. You may have to register to view the article, but registration is free. 


    Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

    Organizations Supporting this Disease

      Learn more

      These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

      In-Depth Information

      • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
      • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
      • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
      • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
      • PubMed is a searchable database of medical literature and lists journal articles that discuss Congenital radioulnar synostosis. Click on the link to view a sample search on this topic.


        1. Anna Siemianowicz, Wojciech Wawrzynek, and Krzysztof Besler. Congenital radioulnar synostosis – case report. Pol J Radiol. Oct-Dec 2010; 75(4):51-54. https://www.ncbi.nlm.nih.gov/pubmed/22802806.
        2. Wurapa R. Radial-Ulnar Synostosis. Medscape Reference. 2016;
        3. RADIOULNAR SYNOSTOSIS. OMIM. May 4, 2009; https://omim.org/entry/179300.
        4. Dogra BB, Singh M & Malik A. Congenital proximal radioulnar synostosis. Indian J Plastic Surg. 2003; 36(1):36-38.

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