Exostosis – Symptoms, Causes, Types


This condition is also known as osteoma. It is a benign growth of new bone on the top of existing bone. The exostosis can happen in many parts of the body. The osteochondroma is a term which is used to describe when the exostosis is covered with cartilage.

This condition can cause irritation or chronic pain which depends on the size and location. When these tiny outgrowths happen in the ear, then they are called surfer’s ears. Also, they can happen under the nail beds or on the heel of the foot. Also, they can develop around the skull, which is including inside the sinuses and mouth. Young adults and children are having highest chances of experiencing exostosis.



Some people can have symptoms of exostosis while others may not have symptoms at all. Many people do not know that they have exostosis until they have an X – ray for another condition and the doctor identifies an area of bony growth. Some people can identify the exostosis because they experience a blockage in a specific area, such as ear canal or in the sinus cavity.

The affected person can start to experience symptoms if the tiny bone growth causes complications, such as pressing on nerves or blood vessels and this can lead to localized pain. Those people who have hereditary multiply exostoses are usually diagnosed by the age of five. They can experience extreme symptoms or no symptoms, such as visibly abnormal bone shapes. This is especially true if these people have osteochondromas because the area of cartilage can harden as the time passes and it can press on nearby blood vessels. The person who has hereditary multiple exostoses can have some of the following symptoms:

  • Limbs of different lengths
  • Pain, especially with movement
  • Shorter height than average
  • Bowed arms or legs
  • Stiffness


The causes for exostosis depend on the location and type of the bone overgrowths. The most common causes for exostosis are chronic irritation of a bone, injury or a family history of exostosis. There are some cases when the cause for exostosis is not known. The exostosis which is related to the family history is called diaphyseal aclasis or hereditary multiple exostoses. In this case, this condition is causing abnormal bone growth on the long bones, such as toes, legs, fingers and arms.


When some person experiences exostosis, then its type will depend on the location. Here are some types of exostosis:

  • Sinuses: The excess bone growth on the walls of the sinuses is known as paranasal sinus osteoma. Sinuses are nasal cavities inside the skull. It is known that this type of exostosis is not always causing symptoms but some people can have long – term or chronic pain and sinus pressure because their sinuses cannot drain properly.
  • Heel of the foot or Haglund’s deformity: This type of exostosis is also known as retrocalcaneal exostosis. This type of exostosis is happening in the back of the heel bone. This type is often made worse by the back of shoe rubbing against the bone for longer period. This is a reason why it is known as “pump bump”. The cause for this type is not known but it is thought that a tight heel, a high arch and genetics are playing a role in it.
  • Mouth or jaw: This type of exostosis is also called buccal exostosis. This is a rare type of exostosis which is causing bony growths from the jaw, usually inside the mouth in the back of the teeth. They often happen from some injury or trauma to the gums and bones underneath.
  • Nailbed: This type of exostosis is also known as subungual exostosis. This is a type of exostosis which is happening when the bony tumor grows underneath the nailbed. It can be caused by an infection or earlier injury and most commonly it affects the big toe. Young adolescents and children are having increased chances of getting this type of exostosis.
  • Ear canal or surfer’s ear: The medical term for this type of exostosis is external auditory canal. It happens in the ear canal. This type happens after repeated cold wind and water exposure and it causes bony growths to develop inside the ear canal.


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