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10th June, 20216 min read

Bone cyst: Symptoms, causes and treatment

Medical reviewer:Dr Adiele Hoffman
Author:Dr Ann Nainan
Last reviewed: 14/05/2021
Medically reviewed

All of Healthily's articles undergo medical safety checks to verify that the information is medically safe. View more details in our safety page, or read our editorial policy.

What is a bone cyst?

Bone cysts are fluid-filled holes that develop inside a bone. They usually aren’t serious, don’t cause any symptoms and some get better on their own without any treatment.

But, if you have a large bone cyst or the cyst starts to cause symptoms, you may need treatment to remove it or drain the fluid from it.

It’s not clear why some people develop bone cysts, but they’re more common in children and teenagers.

Bone cysts aren’t the same as or related to bone cancer, and they don’t spread around the body.

What are the symptoms of a bone cyst?

If you have a bone cyst, you most likely won’t have any symptoms. In fact, often a bone cyst is found by accident during an X-ray for something else.

But larger bone cysts can weaken the affected bone and/or cause symptoms like:

  • broken bones
  • pain – this may happen at night and the pain may get gradually worse
  • swelling or a lump

When to see a doctor about a bone cyst

See a doctor as soon as possible if you have any of the symptoms listed above or you’re worried you may have a bone cyst. They’ll be able to check if you have a bone cyst and recommend the best treatment for you.

Go to a hospital or see a doctor immediately if you have:

  • really bad bone pain especially in your arms, legs, pelvis and chest
  • redness that’s spreading from a part of your body that hurts or feels swollen
  • lost weight without meaning to
  • a fever that doesn’t get better or goes away and comes back
  • trouble moving your arm or leg
  • trouble controlling when you poo or pee

What causes a bone cyst?

The exact cause of bone cysts isn’t known, but there are several different types and each one is thought to have a different cause.

Unicameral bone cysts

Unicameral bone cysts are thought to form from fluid that didn’t drain properly as the bone was growing.

This type of bone cyst usually develops near the ends of the long bones in the arms and legs of children. This end part of a bone is called the growth plate, because it’s the area where growth happens.

Unicameral bone cysts can weaken the long bones they affect, which, in turn, can make that bone more likely to break.

Aneurysmal bone cysts

Aneurysmal bone cysts are slow-growing cysts that are linked to problems with the blood vessels that lie inside your bones. They form blood-filled holes that often sit closely together.

Aneurysmal bone cysts are most common in teenagers. They can affect almost any bone in the body, but they’re often found in the shin bone (tibia), thighbone (femur) or spine.

If you have an aneurysmal bone cyst, you may notice pain and swelling of a body part.

How is a bone cyst diagnosed?

A doctor will usually ask you about your symptoms and any medical conditions you have. They may also look at and feel the area that hurts, is swollen or is causing other symptoms.

Sometimes you’ll only discover you have a cyst when you’ve broken a bone. Read more about the signs of a broken bone.

You may then need to have some tests, including:

What is the treatment for a bone cyst?

If you’ve got a bone cyst, the treatments can vary as cysts have different causes. You may not even need treatment as some cysts can go away on their own.

Treatments can include:

  • regular check-ups and X-rays to make sure the cyst is getting smaller
  • surgery to remove the cyst or to have it drained (aspiration) – aneurysmal cysts usually need surgery as they grow quickly, while unicameral bone cysts can get better on their own
  • medication to help the bone heal, such as steroid injections
  • filling the hole from the cyst with a bone graft or bone cement mixture – a bone graft is when bone tissue is moved from one body part to another part
  • only doing gentle exercise to avoid breaking any weak bones

If you only found out you had a bone cyst when you broke a bone, a doctor will usually let it heal before treating the cyst.

Can you prevent a bone cyst?

Bone cysts usually happen randomly and you can’t do anything to stop yourself from getting one. You may also never know you had one, as they don’t tend to cause problems.

What can you expect if you have a bone cyst?

Most of the time, once a bone cyst has gotten smaller or gone away, you won’t have any further problems with it. However, in some cases, the bone cyst can return, which happens more often with aneurysmal bone cysts.

If you have surgery, it usually takes a few months for a bone to heal completely and you may need to avoid activities or sports that could hurt the bone before it’s healed properly. You may also need regular X-rays to make sure it’s healing well.

Your health questions answered

Can a bone cyst go away on its own?

If a bone cyst is small and not causing you any problems, it may not need treatment. They often get better on their own in children and teenagers. However, you may need regular X-rays for a few years to make sure the cyst isn’t growing and the bone is healing. If the bone cyst is large, getting bigger or causing problems, such as pain, swelling or a lump, it may need to be treated in hospital. Please see a doctor if you think you have a bone cyst or need advice about the management of an existing bone cyst. – Answered by Dr Aleem Qureshi from the Healthily Medical Team

How do doctors remove a bone cyst?

Not all cysts need to be removed. Some will improve and go away on their own. If you find out you have a cyst after you break a bone, you may need to let the bone heal first. If the cyst keeps getting bigger, you may need surgery or to have it drained. After the cyst is removed, you may need a bone graft or medication to help the bone heal.

Is a bone cyst a tumour?

Bone cysts are fluid-filled holes that develop inside of bones. They’re a type of harmless (benign) bone tumour that isn’t serious and some get better on their own. They’re not the same as bone cancer and they don’t spread. They usually don’t cause any symptoms, but you can get pain and swelling from them.

Key takeaways

  • bone cysts are fluid-filled holes that develop inside of bones
  • the exact cause of bone cysts isn’t known, but they’re most often found in teenagers and children
  • bone cysts can have no symptoms, but common symptoms can include pain and swelling in one of your bones
  • the 2 most common types are unicameral and aneurysmal bone cysts
  • some bone cysts will go away by themselves, but some will need treatment, such as surgery and medication
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