Exostosis, also called osteoma, is a benign growth of new bone on top of existing bone. It can occur in many parts of the body. When the exostosis is covered with cartilage, it’s called an osteochondroma.

Exostosis can be painless, or it can cause severe pain and require surgical removal. It frequently shows up in childhood.

The exact cause of exostosis is not yet understood.

You can have an exostosis in your:

  • ear canal
  • ankle
  • jaw
  • sinuses
  • long bones of the leg

Here are some of the leading types of exostosis:

Surfer’s ear

“Surfer’s ear” is a bony growth inside the ear canal. The new bone growth occurs along the part of the ear canal leading to the eardrum. It can occur in one or both ears. As the exostosis develops, it can cause hearing loss.

The cause is not certain, but irritation of the bone by water and wind may facilitate the abnormal growth. Surfer’s ear is usually more serious if you’re a surfer or a sailor. Learn how to get water out of your ear if you’re a surfer or swimmer.

The formal name for surfer’s ear is exostosis of the external auditory canal.

Haglund’s deformity (foot)

Haglund’s deformity is a type of exostosis on the heel of the foot. It’s also known as “pump bump,” because it develops when the stiff back of your shoe rubs against the bump in your heel. Other names for this exostosis are Mulholland deformity and retrocalcaneal exostosis.

A common symptom is pain in the heel that doesn’t go away after resting. It occurs most frequently in middle-aged women and can appear on either or both feet.

Contributing factors include having a tight Achilles tendon, having a high arch in your feet, and heredity.

Paranasal sinus osteoma

The paranasal sinuses are four pairs of sinus cavities, which are the air spaces surrounding your nose. In this type of exostosis, there is an abnormal growth of the bone that forms the sinus cavity.

Often you feel no symptoms. But sometimes, even a small growth can cause a lot of pain. The bone growth can block your sinus from draining properly, causing congestion. It may also cause pain by putting pressure on a nearby nerve.

This type of exostosis is often discovered when you get a sinus scan or X-ray.

Buccal exostosis (jaw)

This is a type of abnormal growth on the upper or lower jawbone. It tends to appear in early adolescence. It’s usually painless, but it might affect the way your mouth looks. It also may get in the way when you’re cleaning your teeth.

Buccal exostosis generally shows up near the back of the mouth, but it may be found in other parts of your mouth.

The cause is not yet known. Genetics may play a role, as may heavy use of the jaw.

Osteochondroma (leg, hip, shoulder)

Osteochondroma is the most common type of noncancerous growth on the bones. It usually has no symptoms, but it may cause other complications.

This type of abnormal bone growth most commonly affects the long bones of the leg, the pelvis, or the shoulder blade. It’s also called osteocartilaginous exostosis.

Osteochondroma affects 1 to 2 percent of the population. It occurs during the growth period of the bone. It’s typically noticed in childhood or the teen years.

Symptoms may include:

  • below-normal height for a child’s age
  • one leg or arm being longer than the other
  • pain during exercise
  • soreness of nearby muscles

Hereditary multiple exostoses (HME)

When more than one abnormal bone growth (exostosis) appears, the cause is usually hereditary. HME is a rare condition that usually shows up in childhood. Sometimes it’s visible to the eye as a lump or protrusion of a bone.

This form of exostosis usually occurs around the long bones of the leg. It sometimes occurs in the upper arm or shoulder blade.

Two other names for this condition are multiple osteochondromatosis and diaphyseal aclasis.

Although exostosis is benign, sometimes complications occur.

For example, complications of surfer’s ear include hearing loss and increased risk of infection. This is because water can collect behind the bony protrusions. Surgical removal of the bony growth by canalplasty is usually successful.

Osteochondromas can also cause problems. An osteochondroma consists of bone surrounded by softer and more pliable cartilage. After developing, the cartilage cap hardens, or ossifies. This hardened cap may cause complications by pressing against surrounding tissue, especially blood vessels.

Some of the complications that may result from an osteochondroma are:

  • Pseudoaneurysm (false aneurysm): This is the collection of blood between the two outer layers of an artery.
  • Claudication: This is a cramping pain, usually in the legs, that may occur after exercise.
  • Acute ischemia: This is a blockage of the blood supply.
  • Phlebitis: This is inflammation of a vein.

There’s about a 1 to 6 percent risk that a benign exostosis resulting from HME can become cancerous. When that happens, it’s called an osteosarcoma.

Exostoses often appear in childhood or the teen years. Some people notice an exostosis and ask their doctor about it.

Your doctor can make a diagnosis based on an examination and sometimes an X-ray or scan. For buccal exostosis, your dentist or periodontist diagnoses the condition by examination and an X-ray.

An exostosis may require no treatment at all. But in some cases, treatment may be necessary.

For surfer’s ear: In more serious cases, surfer’s ear can be treated by an operation known as canalplasty. Wearing ear plugs or a head covering may be a way for surfers to avoid this type of exostosis.

For Haglund’s deformity: Haglund’s deformity occasionally requires surgical removal of the bony growth. Conservative, nonsurgical treatments for Haglund’s deformity include:

  • wearing shoes with lower heels
  • wearing open-backed shoes
  • wearing special orthotics in your shoes
  • getting physical therapy, including massage and ultrasound therapy (a method that’s been used for rheumatoid arthritis)
  • taking anti-inflammatory drugs

For paranasal sinus osteoma: Your doctor may recommend surgically removing the osteoma. This depends on whether you can manage your symptoms without surgery.

Some exostoses show no symptoms at all, while others can require surgery. Here is what to expect for some types:

For surfer’s ear: Symptoms of surfer’s ear can come back even after surgery. In a study of 31 participants, the older the individual, the faster the condition returned. Use of ear plugs was helpful in reducing recurrence.

For osteochondroma: If surgery is performed, complications occur in less than 4 percent of cases of osteochondroma.

For hereditary multiple exostosis: This condition may require no treatment at all. But because there are more affected areas, it’s more likely that it will need a doctor’s attention.