What is Exostosis

By Charlesetta Johnson, Site coordinator

Overview of Exostosis or Saddle Bone Deformity

An exostosis is a bony outgrowth that can occur anywhere on the body. Also known as a bone spur, this condition occurs when a bony growth extends beyond a bone’s usual smooth surface. These bony growths are made of calcium and can appear on any part of the body. The most common exostosis is in the heel and is called a saddle bone deformity. It is  also known as a metatarsal cuneiform exostosis.  Described as the prominence of bone that forms on the top of the foot above the arch.  This condition can develop due to too much movement or mobility in the 1st metatarsal cuneiform joint. Bone formation occurs in an attempt to limit the amount of mobility at this joint.  Pain will develop gradually and will get progressively worse.


They are benign and can vary in shape and size, and can most often be found in the following areas:

  • On the heel or arch (Saddle Bone Deformity)
  • The back of the neck.
  • In between the joints.
  • The sinus cavity.
  • In the ear canal.

A film of cartilage may grow over the exostosis in some people, which is defined as osteochondroma. This is the body’s way of trying to cushion the tissue from the exostosis. It can cause a range of symptoms and be a chronic source of irritation and pain regardless of its size or location.

Image of a patient experiencing pain in the heel.

Also known as a bone spur, this condition can be treated by an orthopedic specialist.

What are the Causes and Types of Exostoses?      

The quick answer can be caused by many different things, ranging from genetics to environmental stress. The type is typically directly related to the cause. When it is related to family history is called hereditary multiple exostoses (HME).

Environmental stresses such as wind and water can cause blockages in the ear canal (surfer’s ear) and sinus cavity (paranasal exostosis), leading to bony outgrowths. Wearing certain shoes such as high heels or narrow footwear may irritate an individual’s foot, causing this condition to form. Haglund’s deformity and Saddle Bone’s deformity are examples of exostoses that can appear on foot.

Damage to a person’s joints causes strain on the joints, leading to this condition in that specific joint. Osteocartilaginous exostosis, also referred to as an osteochondroma, involves cartilage and bone growth and normally appears at long bones’ ends.

What are the Symptoms of Exostosis?

Pain is a common symptom, ranging from mild to debilitating. The pain level is most often dependent on the size, shape, and location of the exostosis. A person may start to experience symptoms if the condition is causing complications, such as pressing on blood vessels or nerves, leading to localized pain.

A person with hereditary multiple exostoses may experience stiffness, limb length discrepancies, or pain. Sometimes, people who have an exostosis may have no symptoms and are not aware of their condition until they have an X-ray.

How Do You Diagnose and Treat an Exostosis?

A physician can identify an exostosis from examining the patient, taking a family history, and x-rays. Once the physician determines the cause and extent of the exostosis, a treatment plan will be provided. Conservative treatment, such as Physical Therapy, can help resolve the painful symptoms and decrease the inflammation of the tissue that is irritated by this condition.

However, Physical Therapy can not decrease or reduce the size of the exostosis. If the exostosis painful or aesthetically displeasing, the physician might recommend surgery as a treatment option.

If you feel you may be suffering from exostosis, our dedicated team of orthopedic specialists is ready to help you! To schedule an appointment, call JOI-2000 or click the button below to schedule an appointment online.

What is Exostosis? Also known as a bone spur, this condition can be treated by an orthopedic specialist.

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By: Charlesetta Johnson

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