Osteochondroma: Decoding That Bone Bump

By Dr. Priya Sammani ( MBBS, DFM )

It’s a moment, isn’t it? You’re just going about your day, or perhaps you’re checking on your child, and then you feel it – a firm, unexpected little bump on a bone. Your heart might do a little flip. What on earth is that? Well, sometimes, these discoveries lead us to something called an osteochondroma. It sounds a bit complicated, but let’s break it down.

I often tell my patients that an osteochondroma is essentially an overgrowth of cartilage and bone, usually showing up near the ends of the long bones – think legs, arms. If you picture a child or teenager who’s still growing, they have areas called growth plates at the ends of their bones. These are like busy little factories making new bone. An osteochondroma is like a bit of that factory material decided to grow outwards, forming a benign (that means noncancerous, which is good news!) tumor. They typically pop up during childhood or teenage years and then, just like the rest of the skeleton, they usually stop growing once a young person reaches their full height.

So, What Kind of Osteochondroma Are We Talking About?

There are mainly two ways these can appear, and we think of them as slightly different situations:

  • Solitary Osteochondroma: This is the most common scenario – just one single growth. Often, it’s a bit of a surprise find; we might spot it on an X-ray we’re doing for a completely different reason! The exact cause? We’re not entirely sure. It’s not from an injury. There’s some thought it might have a genetic link, but it’s still a bit of a puzzle. Because it’s benign, it doesn’t spread elsewhere in the body. Another term you might hear is osteocartilaginous exostosis – “exostosis” just means an outward growth of bone.
  • Multiple Osteochondromas: This is less common, happening in about 15% of cases. When someone, often a child, has several of these growths, it’s usually due to an inherited genetic condition we call hereditary multiple osteochondromas (or hereditary multiple exostoses). Though, sometimes, even multiple ones can just happen randomly without a clear family link. These are also noncancerous, but having several can sometimes lead to a few more challenges, especially with how bones grow.

Is an Osteochondroma a Big Worry?

Generally, no, it isn’t. For a single osteochondroma, if it’s not causing any trouble, we often just keep an eye on it. Treatment isn’t usually needed unless it starts pressing on nearby nerves, blood vessels, or other bones, causing discomfort. There’s a tiny chance, about 1%, that an osteochondroma could become cancerous over time (turning into something called a chondrosarcoma – a cancer of the cartilage cap). That’s why we like to monitor them.

Now, if you’re a parent and we’re looking at hereditary multiple osteochondromas in your child, the situation can be a bit more involved. These can sometimes affect how bones develop, perhaps leading to a limb looking a bit different, or causing some discomfort. The risk of one of these turning cancerous is a little higher, around 5%, so we watch these cases more closely.

Just to be clear, if an osteochondroma were to become cancerous, it’s the cartilage part that changes – that’s chondrosarcoma. This is different from osteosarcoma, which is a cancer that starts in the bone itself.

You might wonder where these bumps usually show up. Knees are a very common spot – about 40% of them are found there. But they can appear near the hip, shoulder, or really any bone that has cartilage and is growing.

What Clues Might Point to an Osteochondroma?

Many times, there are no symptoms at all! It’s just… there. But if you do notice something, it might be:

  • A small, hard, painless lump you can feel under the skin, close to a bone.
  • Aching or pain with certain movements, especially if the growth is rubbing against a nearby tendon.
  • A sensation of numbness or tingling if it’s putting pressure on a nerve.
  • Rarely, changes in blood flow to a limb if a blood vessel is being squished.

For children with the multiple kind, we might see:

  • Them being a bit shorter than expected for their age.
  • A limb that looks a little crooked.
  • One arm or leg being noticeably longer than the other.
  • Sometimes, issues with the hip joint, like hip dysplasia.

And what if we’re worried it might be changing? We’d pay close attention if:

  • The lump starts causing pain for no clear reason.
  • It keeps growing after your child has stopped growing.
  • In an adult, if the cartilage cap on the tumor looks thicker than about 1.5 cm on an imaging scan.

How Do We Figure This Out? Getting a Diagnosis

If you come to me with a suspicious lump, or if you’re a parent worried about your child, we’ll start by talking. I’ll ask about any symptoms, when you noticed it, and your family history. Then, a physical exam helps me get a better sense of things.

To really see what’s going on, we usually turn to imaging.

  • An X-ray is often the first step. Osteochondromas usually show up quite clearly on an X-ray.
  • If we need a more detailed look, perhaps to see the cartilage cap or how close it is to nerves or blood vessels, we might suggest an MRI (Magnetic Resonance Imaging) or a CT scan (Computed Tomography scan). These give us more detailed pictures.

What’s the Plan? Treatment for Osteochondroma

So, what do we do about an osteochondroma? Often, the answer is… not much at all, especially for a single one that isn’t causing any bother. We might just recommend keeping an eye on it with occasional X-rays. And, of course, letting us know if any new symptoms pop up.

If it is causing problems – like pain, limiting movement, or if there’s any concern about it changing – then surgery to remove it might be the best option.

For children with multiple osteochondromas, we’ll monitor them more regularly. We want to track any new growths and see how they might be affecting bone development. If a tumor is interfering with growth or causing significant issues, we’d likely recommend removing it. Sometimes, other surgeries might be needed to help realign bones if they’ve grown unevenly.

Surgery itself is usually straightforward. It’s done under general anesthesia, meaning you’ll be asleep. The surgeon makes a small cut over the tumor and carefully removes it. Most people can go home the same day. If the tumor is in a tricky spot near important blood vessels or nerves, it can be a bit more complex, but we’d talk all that through with you.

Recovery is generally quite good. Many folks are back to their usual activities pretty quickly. Sometimes, especially if it was a leg bone, we might suggest using a sling or crutches for a bit to take the weight off. We’ll also make sure you have a plan for managing any discomfort in the first few days.

And the big question: can it come back? If an osteochondroma is completely removed, it usually doesn’t grow back. There’s a small, about 5%, chance of a new one appearing in the same spot in very young children who have the multiple type. But remember, these growths typically stop growing once the skeleton is mature.

Interestingly, very rarely, an individual osteochondroma might just decide to shrink and get reabsorbed by the bone all on its own. Why this happens, we don’t quite know. It’s not common, but it’s a little quirk of these growths.

Key Things to Remember About Osteochondroma

Alright, that was a lot of information! Here are the main points I’d like you to take away about osteochondroma:

  • It’s a benign (noncancerous) growth of bone and cartilage, most often found near the ends of long bones in growing children and teens.
  • Many cause no symptoms and are found by chance.
  • If symptoms occur, they might include a hard lump, pain with movement, or nerve pressure.
  • Diagnosis usually involves an X-ray, and sometimes an MRI or CT scan.
  • Treatment isn’t always needed. Surgery is considered if it’s causing pain, affecting function, or if there are any concerns about changes.
  • The chance of it becoming cancerous is very low, but we do monitor them.
  • Hereditary multiple osteochondromas is a genetic condition that needs closer monitoring, especially in children, as it can affect bone growth.

A Final Thought

Discovering any kind of lump can be unsettling, I know. But with osteochondroma, the outlook is generally very positive. The most important thing is to get it checked out so we know what we’re dealing with. We’re here to walk you through it, every step of the way. You’re not alone in this.

Dr. Priya Sammani
Medically Reviewed by
MBBS, Postgraduate Diploma in Family Medicine
Dr. Priya Sammani is the founder of Priya.Health and Nirogi Lanka. She is dedicated to preventive medicine, chronic disease management, and making reliable health information accessible for everyone.
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