What is it?

Radioulnar synostosis is a rare condition in which the two bones of the forearm- the radius and the ulna- are abnormally connected. This limits rotation of the arm. Radioulnar synostosis is usually congenital. It can also occur as the result of a forearm fracture or trauma.

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Signs & symptoms

Congenital radioulnar synostosis can be mild to severe. The telltale symptom is a limitation in your child’s ability to rotate their forearm from a palms-down (pronated) position to a palms-up (supinated) position. A child with radioulnar synostosis may also carry their elbow at an abnormal angle and their forearm may be short or bowed.

In severe cases, the bones are connected and the forearm is fixed in one position, usually with the palm facing down to some degree. Depending on the position of the forearm and the flexibility of your child’s wrist, their activity may be limited in ways that are either subtle or noticeable.


If the child was born with mild radioulnar synostosis, the condition may not be noticeable and may not be diagnosed until your child reaches school age. In some children, mild radioulnar synostosis is not diagnosed until adolescence.

If the child has a more severe form of the condition, their forearm rotation will be much more limited and the condition will be more obvious. In such cases, the condition can be diagnosed at an earlier age- typically around age 6.

To diagnose radioulnar synostosis, the child’s doctor will do a thorough medical history and physical exam. They may order an x-ray and/or a CT scan. The images will help them assess the underlying structure of your child’s bones, confirm the diagnosis, check for related conditions, and determine a course of treatment.


Treatment depends on whether your child is having problems using their arm. Some children with radioulnar synostosis never need surgery. Physical and occupational therapy can help the child meet normal developmental milestones and work around any activity limitations.

If the child has radioulnar synostosis in both arms, or if their forearm is fixed in a position that limits the function of their arm, they may benefit from surgery. Surgery is usually performed before children reach school age.

☝️ This is not a substitute for professional medical advice. Please consult with your physician before making any medical decision.

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