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Definition: What is Exostosis?

This is a bony outgrowth that can occur anywhere on your body and is non-cancerous. It is basically the formation of new bone on the surface of another bone. You will mainly notice them on your ribs but you may see larger growths on your shoulders, knees, ankles, hips, elbows, jaw, but never on your skull.

Exostosis Symptoms

Other than it could become painful the symptoms that exostosis might cause would be related to the cause. The pain a person feels from having any form of exostosis can range from mild to debilitating severe. The pain depends on where the exostosis is located, the size, and shape.

  • Surfer’s ear – with this cause, which is considered environmental stress, causes a person to have difficulty with hearing. They may also have pain in their ears caused by the growth
  • Subungual exostosis – with these they are usually painful because of the pressure that is applied to the nail plate and bed. They can also destroy your nail bed
  • Buccal exostosis – this type is painless
  • Retrocalcaneal exostosis – this is a painful bump and you may also have tenderness, swelling, or redness along the bony prominence on the back side of your heel. The pain usually becomes worse when wearing shoes that rub the back of your heel or with any type of activity. There can also be pain at the insertion site of your Achilles tendon on the back of your heel bone
  • Dorsal exostosis – this type is often very painful. With dorsal mid-foot exostosis if you wear the wrong shoes and cause the bump to rub against the top of the shoes you may notice swelling and redness of the bump. With dorsal exostosis of the big toe joint you may experience range of motion limitations, limited extension of the big toe, and pain
  • Metatarsal cuneiform exostosis – pain with direct pressure from your shoes and is described as a dull ache that radiates between your first and second toes.


An exostosis can be caused by many different things ranging from genetics to environmental stress.

  • Environmental stress – one example of this is if the bone grows into your ear canal and becomes known as surfer’s ear. This is caused by frequent flooding of your ear with cold water
  • Damage to your joints – with this cause the strain on your joints will result in the development of a small deposit of bone near or on the joint.
    Excess calcium buildup.

Sometimes there is no clear environmental cause and it just occurs spontaneously.

Subungual exostosis

This type of exostosis involves your fingers and toes. They usually arise from the dorsal, or back, surface of your distal fingers or toes. This means outermost bone on your toe or finger. You will normally find them growing under the nail, especially your toenail of the big toe. They are less common on your fingers but when they occur there it is usually on your middle and index fingers. The exact cause is not known but they can occur because of some trauma to the toe. It is also thought that having a chronic infection or constant irritation can cause them. They can occur at any age but more cases occur by twenty years of age and are more prominent in females.

Buccal exostosis

This type of exostosis involves your jawbone. In this case your lower jaw will be more prone than your upper jaw. It forms on your outer cheek facing the side of your upper jaw just above your teeth. It could also affect the cheek-facing side of your lower jaw. It is much less common to find it on your lower jaw than on the upper jaw. They usually start to form in early adulthood and over time slowly enlarge

Retrocalcaneal exostosis

This is a bone spur or bump on the back of your heel bone and often involves your Achilles tendon. It is a problem that affects most adults, especially women because of the types of shoes they wear. The shoes that irritate this bony growth the most are pumps or very high heeled shoes. They can also occur because of short or tight Achilles tendon, inflamed pad, bursitis, inflammation, Haglund’s deformity, or Achilles tendonitis.

Dorsal exostosis

This is a distinct bump on the top of your foot and is often referred to as dorsal mid-foot exostosis. Having this type can make wearing some shoes very difficult. If they are open-toed they will usually pose no problems but if you wear enclosed shoes it can cause the bump to compress and rub against the top of your shoe. It can also be caused by rolled-in feet but can also occur in people who have high arches. Injury and trauma to the area can also cause this bony bump. You can also get dorsal exostosis of the big toe joint and is similar to bunions. Dorsal exostosis of the big toe can be cause due to biomechanical factors that can alter the alignment of your foot, tight calf muscles that force your arch to say, or trauma to the joint of the big toe.

Metatarsal cuneiform exostosis

This is often referred to as a saddle bone deformity and is a prominence of a bone that forms on the top of your food above your arch. It can happen because of hyper-mobility in your first metatarsal cuneiform joint, which are three different bones that are side-by-side in your mid-foot and lead to the base of each toe. You usually see this between the ages of twenty-five and sixty and are found equally in women and men.

Osteocartilaginous exostosis

This cause involves a growth of cartilage and bone and is also referred to as osteochondroma. This type normally appears at the ends of your long bones.

Hereditary multiple exostosis (HME)

This is when exostoses randomly occur across your body because of an inherited condition. If you have a family history of HME you should monitor your children as they develop in order to detect early any signs of bony growths. This cause is estimated to affect one in fifty thousand people. Most are unaffected at birth but by the age of twelve they begin to develop multiple ones.


It can be identified by your physician from an examination, taking a family history, and x-rays.


Once your physician has determined the extent of the exostosis and the cause then they will talk with you about treatment options. In some cases the growth may be allowed to remain but it becomes aesthetically displeasing or painful surgery is a treatment option. If surgery is done your physician will talk with you about the cause to see what can be done or modified to help prevent it from recurring. When it is allowed to remain your physician will check it often to identify any signs of complication that could emerge.

  • With osteochondroma, this non-cancerous tumor can be removed or left in place. It all depends on whether it interferes with your quality of life.
  • If the cause of exostosis is surfer’s ear, a surgeon can remove the bone in order to give you more comfort and restore hearing.
  • Subungual exostosis — treatment for this type is surgical excision and is very effective. It is done under local anesthesia and once the growth is removed the underlying bone is scraped clean to prevent it from recurring.
  • Retrocalcaneal exostosis — how it is treated will depend on the severity of the pain. To help with the inflammation of the tendon you may be given a prescription for steroids or an oral NSAID. You may also be given a prescription for an adhesive pain patch or pain gel that you can apply to the back of your heel. Your physician may order heel lifts, which are a wedge that goes under your heel to lift it so the tension on your Achilles tendons decreases. This heel lift can also raise your heel out of your shoe a little so the back of the shoe is not rubbing on the painful spot. For severe pain you may have to have your foot immobilized in a walking boot to decrease the strain and stress on your Achilles tendon. The last option for severe pain is to put your foot in a cast and have you use crutches so you do not put any weight on the foot. Your physician may also have you undergo physical therapy to decrease the inflammation of the tendon and increase the flexibility of your Achilles tendon. If all of these non-surgical methods do not help then you may have to have surgery.
  • Dorsal exostosis — with dorsal mid-foot exostosis you should modify your footwear to avoid compressing the bump. For rolled-in feet and high arches you may need orthotic therapy. Your physician may give you a prescription of anti-inflammatory medication or have you take some over-the-counter anti-inflammatory medication. To help provide relief to the joint and nerves your physician may use injection therapy. Having surgery would be the final treatment if nothing else works or the pain becomes unbearable. With dorsal exostosis of the big toe in order to improve foot function you need to do stretching exercises, correct the biomechanics that caused the problem, and orthotics. Any of these will ease the stress on the big toe joint. Again, if non-surgical treatment does not work then you may need surgery to clean the big toe joint up.
  • Metatarsal cuneiform exostosis — the best treatment is to wear shoes that put no pressure on the bony bump. These can include low cut dress shoes, flip-flops, or sandals. You can also use a tongue pad to create a small area on the underside of the shoe tongue to relieve pressure on the bump. If surgery is needed it will be done in a surgery center or hospital under general anesthetic or sedation and local anesthesia. After surgery you can put weight on the foot but can take approximately four to six weeks before you can return to normal activities.

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