Exostosis: Causes, Treatment, and More

Bones are supposed to be the quiet, reliable friends of your bodystrong, supportive, and not at all interested in drama. And then sometimes a bone decides to grow a little extra… like it’s trying out for a “Most Improved Skeleton” award. That extra bump of bone is often called an exostosis.

Most exostoses are benign (not cancer), many don’t cause symptoms, and a lot of people discover them by accident on an X-ray done for something totally unrelated. But some can irritate nearby tissues, trap water in an ear canal, press on a nerve, limit joint motion, or just be plain annoyingespecially when they show up exactly where your shoe rubs or your tendon glides.

What is exostosis?

Exostosis is a general term for a noncancerous bony outgrowtha new growth that forms on the surface of an existing bone. Think “extra bone,” not “extra bone marrow” and not a separate bone floating around like a spare key.

The word is broad on purpose. In everyday healthcare conversations, “exostosis” can refer to several related things, including: bone spurs (osteophytes), osteochondromas, and location-specific growths like “surfer’s ear” (ear canal exostoses) or oral tori (bony bumps in the mouth).

Exostosis vs. bone spur vs. osteochondroma

• Bone spur (osteophyte): A type of exostosis commonly linked to joint wear-and-tear (often osteoarthritis). It’s usually near a joint.
• Osteochondroma: A cartilage-capped bony growth that often develops near growth plates in children and teens. It’s one of the most common benign bone tumors.
• Exostosis: The umbrella term that can include both of the aboveplus other “bonus bone” scenarios depending on location and cause.

Common types of exostosis (with real-world examples)

1) Bone spurs (osteophytes): the “joint’s safety railing” that sometimes gets in the way

Bone spurs are extra bone growths that can form where there’s ongoing stress, friction, inflammation, or joint damagemost often from osteoarthritis. Many bone spurs cause no symptoms and don’t require treatment. When they do cause trouble, it’s usually because they irritate surrounding tissues or crowd the space where tendons, ligaments, or nerves need to glide freely.

Example: A person with a stiff, achy big toe joint may develop a spur that rubs inside the shoe and makes walking feel like every step is a tiny complaint letter. Or someone with spine arthritis might have spurs that contribute to nerve irritationone reason certain spine procedures aim to relieve pressure.

2) Osteochondroma: common in kids and teens, often found near the knee or shoulder

An osteochondroma is a benign growth that often appears near the ends of long bonescommonly around the knee or shoulder. Many are painless and discovered incidentally. Sometimes they cause pain during activity, a snapping tendon sensation, numbness/tingling if a nerve is compressed, or visible bumps.

These growths often develop during the growing years and typically stop enlarging once growth plates close. That’s why clinicians pay close attention if a known osteochondroma seems to grow or become more painful later in adulthood.

3) Hereditary multiple osteochondromas (multiple hereditary exostoses): when genetics gets involved

Some people develop multiple osteochondromas because of a genetic condition often called hereditary multiple osteochondromas (also known historically as multiple hereditary exostoses). It’s commonly associated with changes in genes such as EXT1 or EXT2 and is often diagnosed in childhood. Because multiple growths can affect bone development, this condition may lead to limb length differences, deformities, restricted motion, or nerve compression.

While the overall risk of malignant change is still low, it’s generally considered higher in people with multiple hereditary osteochondromas than in those with a single lesion. This is why ongoing follow-up matters for some families.

4) “Surfer’s ear” (external auditory canal exostosis): cold water, wind, and the ear canal’s stubborn response

“Surfer’s ear” is a nickname for exostoses in the external ear canal. It’s linked to repeated exposure to cold water and wind. The body’s response to chronic irritation can stimulate bone-forming cells, gradually narrowing the ear canal.

Common complaints: muffled hearing, a feeling of fullness, water getting trapped, and more frequent ear infections. Mild cases are often managed with protection (like earplugs), while significant blockage may require a surgical procedure called canalplasty to remove the excess bone. If cold-water exposure continues without protection, recurrence is possible.

5) Oral exostoses (tori): harmless mouth bumps with an unfortunate knack for showing up during flossing

Torus palatinus is a bony growth on the hard palate (roof of the mouth), while mandibular tori are bony bumps on the inside of the lower jaw. Many people never need treatment. Removal may be considered if the growth interferes with speech, chewing, swallowing, dental appliances, or comfort.

6) Other location-specific forms

• Subungual exostosis: A bony growth under a fingernail or toenail bed (often painful because… well, toenails do not enjoy surprise roommates).
• Paranasal sinus exostosis: Bony growths in sinus regions that may be found incidentally on imaging.
• Heel spurs: Often associated with long-standing plantar fascia stress; not always the true source of heel pain, but frequently shows up on X-ray.

What causes exostosis?

There isn’t one single cause because exostosis is a category, not one disease. Still, most causes fall into a few common themes: mechanical stress, chronic irritation, inflammation, injury, and genetics.

Common cause patterns

• Joint damage and osteoarthritis: Wear-and-tear can lead to osteophytes (bone spurs), especially around joints.
• Repeated irritation: Classic example: cold water/wind exposure contributing to ear canal exostoses.
• Growth-plate related development: Osteochondromas typically arise during childhood/teen years, often near growth plates.
• Inherited genetic conditions: Hereditary multiple osteochondromas is linked to gene changes (commonly EXT1/EXT2).
• Local stress points: Feet, toes, and areas under nails can develop painful exostoses because pressure and microtrauma add up over time.

Symptoms: when an exostosis matters (and when it doesn’t)

Many exostoses are silent. They exist. They chill. They get discovered when someone gets imaging for a sprain, a dental exam, or a random sports injury. Symptoms usually happen when the growth interferes with movement, compresses structures, or creates irritation.

Possible symptoms

• A firm bump on a bone (often painless)
• Pain with activity (especially if a tendon rubs or “snaps” over the bump)
• Numbness or tingling if a nearby nerve is compressed
• Reduced range of motion or joint stiffness
• Ear issues: muffled hearing, water trapping, recurrent ear infections (ear canal exostoses)
• Mouth irritation or difficulty with dental appliances (oral tori)
• Shoe irritation and pressure pain (foot/toe exostoses)

Red flags that deserve prompt medical attention

• New or worsening pain that doesn’t match your usual pattern
• A bump that seems to grow quickly, especially after you’re done growing
• Night pain or pain at rest that persists
• New weakness, persistent numbness/tingling, or circulation changes
• Repeated infections (for ear canal narrowing) or significant hearing changes

How is exostosis diagnosed?

Diagnosis usually starts with a history and physical exam. A clinician will ask about pain, growth, activity triggers, family history, and functional problems. Then imaging helps confirm what the bump is and what it’s doing to nearby structures.

Common tests

• X-ray: Often the first step; it can show bony outgrowths clearly.
• CT scan: Useful for complex anatomy (like the ear canal or sinuses) or surgical planning.
• MRI: Helpful when evaluating cartilage caps, soft tissue involvement, or nerve/vessel proximity.

For hereditary multiple osteochondromas, diagnosis may involve clinical patterns, imaging, and sometimes genetic evaluationespecially when multiple family members are affected or when there are multiple lesions in childhood.

Treatment: from “do nothing” to surgery (with plenty in between)

Treatment depends on the type, location, and symptoms. A painless, stable exostosis might need nothing more than occasional monitoring. A growth that causes pain, nerve compression, infections, or functional problems may need active treatment.

1) Observation (watchful waiting)

If you have no symptomsor mild symptoms that are stableclinicians often recommend monitoring. This is especially common with solitary osteochondromas that aren’t causing nerve/vessel issues.

2) Conservative care (the “let’s calm things down first” plan)

• Activity modification: Reduce movements that flare pain or irritation.
• Pain relief: Over-the-counter anti-inflammatory medications may help when appropriate.
• Physical therapy: Strength and mobility work can reduce stress around affected joints.
• Supportive gear: Orthotics, better footwear, or pads can reduce pressure from foot-related exostoses.
• Protection for swimmer/surfer’s ear: Earplugs or protective hoods help reduce cold-water exposure and slow progression.

3) Procedures and surgery (when the bump won’t behave)

Surgery is usually considered when there’s significant pain, functional limitation, recurrent infections (in ear canal narrowing), deformity concerns, nerve/vessel compression, or features that raise concern for atypical change.

• Excision of an osteochondroma: Removal of the growth can relieve pain, snapping tendons, or nerve symptoms. For suspicious lesions, surgeons may evaluate the tissue carefully.
• Canalplasty for ear canal exostoses: A procedure to remove bony overgrowths and reopen the ear canal. It’s typically done under anesthesia; recovery and precautions vary by case.
• Oral surgery for tori: Considered if the growth interferes with speech, chewing, swallowing, or dental workotherwise often left alone.

Recovery: what to expect

Recovery depends heavily on location and procedure. In general, people can expect a period of rest, gradual return to activity, and follow-up visits to ensure healing and symptom improvement. Some exostoses can recur if the underlying trigger continues (for example, continued cold-water exposure after ear canal surgery without protection).

Prevention and self-care

You can’t prevent every form of exostosisespecially those tied to geneticsbut you can often reduce risk or slow progression by managing the triggers. Consider these practical strategies:

Smart prevention moves

• Protect ears in cold water: Earplugs or a hood can reduce chronic cold-water/wind irritation.
• Support joints: Strength training, mobility work, and low-impact exercise can help joints function better over time.
• Manage osteoarthritis factors: Weight management, activity adjustments, and clinician-guided care can reduce stress that contributes to spurs.
• Foot-friendly habits: Wear supportive shoes, address biomechanical issues, and avoid repetitive pressure points when possible.
• Don’t ignore persistent symptoms: Early evaluation can prevent a small mechanical problem from becoming a big functional one.

When should you see a doctor?

If you notice a new bony lump, persistent pain, numbness/tingling, restricted movement, hearing changes, or repeated ear infectionsget evaluated. Most causes are benign, but it’s worth confirming what you’re dealing with, especially if symptoms are changing.

And if you already know you have an exostosis or osteochondroma, contact a clinician sooner if the bump becomes painful, seems to enlarge, or starts interfering with daily activities. It’s not “being dramatic”it’s being smart.

FAQ

Is exostosis cancer?

Exostosis itself usually refers to a benign bony growth. However, clinicians take changing symptoms seriouslyespecially new growth or pain after skeletal maturitybecause a small subset of bone tumors can be malignant or become concerning over time.

Does an exostosis go away on its own?

Generally, once bone forms as an exostosis, it doesn’t “melt away.” Symptoms can improve if inflammation around it calms down, if pressure is reduced, or if mechanics improve. Some conditions are managed by preventing progression and treating irritation.

Can exercise cause bone spurs or exostosis?

Exercise itself isn’t the villain. But repetitive stress, poor mechanics, and chronic irritation can contributeespecially around joints or tendon insertions. The goal isn’t “stop moving,” it’s “move smarter,” ideally with good support and technique.

If I have a family history, should I worry?

A family history can matterparticularly for hereditary multiple osteochondromas. If multiple relatives have bony growths, deformities, or childhood-diagnosed osteochondromas, it’s worth discussing with a clinician who can guide evaluation and follow-up.

Experiences: what people notice, what helps, and what surprises them (extra section)

The medical definition of exostosis is tidy. Real life is not. People often describe the experience as less “dramatic disease” and more “Why is my body installing a speed bump right there?” Below are common, realistic experiences patients reportpresented as generalized composites, not anyone’s private story.

Experience 1: The teen athlete who finds a bump near the knee

A common scenario: a teenager notices a hard, painless bump near the knee after practice. It doesn’t hurtuntil it does, usually during certain movements, or when a tendon glides over it and creates a weird snapping sensation. Many teens feel fine and keep playing sports, but the bump becomes a “constant curiosity.” A clinician orders an X-ray, and the report suggests an osteochondroma.

What tends to help most here isn’t panicit’s context. Many osteochondromas are benign and simply monitored. People often feel relieved to learn that “tumor” doesn’t automatically mean cancer and that growth tends to slow after growth plates close. When symptoms do appear, athletes often benefit from targeted strengthening, flexibility work, and practical adjustments (like modifying training load). If nerve symptoms show uptingling, numbness, or weaknessevaluation becomes more urgent, and surgery may be discussed.

Experience 2: The surfer/swimmer who keeps getting ear infections

This experience is almost unfairly predictable: someone who loves cold-water surfing starts noticing that water gets stuck in the ear more easily. Then come the infections, the muffled hearing, the “my ear feels full,” and the awkward head-tilting dance people do to drain water that refuses to cooperate. Eventually they’re told they have ear canal exostosesaka surfer’s ear.

The biggest “aha” moment for many people is realizing it’s not about being tough; it’s about physics and anatomy. Wearing earplugs can feel annoying at first, but many people report it’s a game-changer: fewer infections, less trapped water, and less progression. For those who need surgery, the best surprise is often how much clearer things sound afterward. The most annoying surprise? If they go right back to cold water with zero protection, the problem can come back. The ear canal remembers.

Experience 3: The adult who thinks a bone spur means “I’m falling apart”

Many adults find out about bone spurs after imaging for back pain, knee pain, or a stiff toe. The phrase “bone spur” can sound ominous like your skeleton is growing thorns. In reality, many spurs are common with aging and arthritis and don’t cause symptoms. The symptoms often come from inflammation, joint mechanics, or irritated soft tissue rather than the spur itself.

People who do well long-term often shift from “How do I delete this spur?” to “How do I reduce the stress that keeps irritating this area?” That can look like physical therapy, strength training, weight management when applicable, better shoes, orthotics, and pacing activities. Some people discover that a few small habit changeswarming up, avoiding repeated high-impact overload, improving mobilitycan cut symptoms dramatically. Surgery is usually not the first step, and many folks are relieved to learn that “last resort” really does mean last resort.

Experience 4: The person who discovers mouth tori during a dental visit

Oral tori can be funny in an un-funny way: they’re usually harmless, but once you know they’re there, you can’t un-know it. Some people notice them because a dental appliance doesn’t fit well, or they keep bumping the area while brushing. The most common emotional arc is: “Is this serious?” → “Oh, it’s benign.” → “Cool, but can it stop existing where my tongue likes to roam?”

Most people do nothingand that’s the correct plan if it’s not interfering with function. If removal is needed for dental work or discomfort, people often report the recovery is manageable, and the biggest benefit is simply not thinking about that bump every time they floss. (Flossing already has enough going on.)

Takeaway from real-life experience

Exostosis often isn’t about “something terrible happening.” It’s frequently about location, mechanics, and irritation over time. When symptoms show up, the best outcomes usually come from a mix of good evaluation, conservative care first, and surgery only when the bump is truly causing harm or blocking function. And yessometimes the most effective treatment is as simple (and as unglamorous) as wearing the right shoes or using earplugs.