Bone Cyst

Overview

A bone cyst is a fluid-filled space that develops inside a bone. Most bone cysts are not cancerous, and many cause no problems. They are usually found by chance when an X-ray is done for another reason.

Bone cysts are fairly uncommon. They make up a small number of all bone lumps, but they are the most common type of benign (non-cancerous) bone cyst in children and young people.

Simple bone cysts are most often diagnosed in children and teenagers aged 5 to 15 years. Aneurysmal bone cysts can occur at any age but are also most common in teenagers and young adults. Adults are less often affected.

Symptoms

Common symptoms

• No symptoms at all — many cysts are found only when an X-ray is done for another reason.
• A dull, aching pain in the affected bone.
• Mild swelling if the cyst is near the skin surface.
• A recent bone break (fracture) in the area of the cyst.

Symptoms in children

• A limp or favoring one leg if the cyst is in the leg.
• Unexplained pain, especially at night.
• A fall or knock that leads to a bone break — this can be the first sign.

Symptoms in older adults

• Pain in the affected area that may worsen with activity.
• A bone break that seems to happen very easily or with little trauma.
• Less commonly, swelling or a feeling of pressure in the bone.

Causes

Main causes

• The exact cause is not fully understood.
• Most bone cysts do not appear to be inherited and are not passed on in families.
• Simple bone cysts may develop due to abnormal drainage of fluid in the bone.
• Aneurysmal bone cysts may be linked to small blood vessel problems in the bone.

Risk factors

• Being a child or teenager during growth spurts.
• Being male — simple bone cysts are about twice as common in boys.
• A previous injury to that area, though this is not proven for all types.

When to see a doctor

See a doctor urgently if:

• You or your child have sudden, severe bone pain with difficulty moving.
• A limb looks deformed.
• Numbness or tingling beyond the bone.
• You have bone pain and a fever.

Book a routine appointment if:

• A dull ache in a bone that lasts more than a few days.
• You or your child have a new limp.
• You notice a firm swelling over a bone.
• You have a bone break and an X-ray shows a cyst at the same spot.

Diagnosis

A bone cyst is usually first seen on an X-ray. Because the cyst is not dense like normal bone, it appears as a clear, hollow space in the bone. Your doctor may refer you to an orthopaedic specialist (a bone doctor) for further tests.

Tests that may be done

• X-ray — the first and most common test.
• Magnetic resonance imaging (MRI) — gives a detailed picture of the cyst and surrounding tissues.
• Computed tomography (CT) scan — shows the bone structure in 3-D.
• A bone scan or blood tests — sometimes used to rule out other bone problems.
• Biopsy — a small sample of the cyst is taken if there is doubt about the type.

What to expect at your appointment

You will usually be asked about your symptoms and any recent injuries. The doctor will examine the area. Most people who see a GP for a bone cyst do not need an urgent scan; the doctor will arrange an X-ray and refer you to a bone specialist if needed. The specialist will explain what the scan shows and discuss the next steps with you.

Treatment

Treatment depends on the type of cyst, its size, where it is, and whether it is causing symptoms. Some cysts heal on their own. Others may need a small procedure to drain the fluid or reinforce the bone. The main goals are to prevent fractures, ease pain, and keep the bone healthy.

Self-care at home

• Rest the area if you have mild pain — avoid high-impact sports until a specialist gives the all-clear.
• Use over-the-counter pain relief (ask your pharmacist which is safe for you or your child).
• Wear supportive shoes and take care on uneven ground to reduce falls.
• Apply a cold pack for 15–20 minutes if there is mild swelling — always wrap it in a cloth.

Medical treatments

If a cyst is at risk of causing a fracture, an orthopaedic specialist may recommend a procedure. This can include draining the fluid with a needle (aspiration) and injecting a substance that helps the bone heal. The choice of injectable material depends on the case. Sometimes the cyst is scraped out and the remaining space is filled with bone graft or a special cement. The exact method depends on the individual situation, and your doctor will explain the options in plain language.

When is surgery considered?

Surgery is usually considered when the cyst is large, is growing, has caused a fracture, or is in a position where a fracture would be dangerous. Surgery may not be needed if the cyst is small and stable. Children's cysts sometimes respond to a simpler needle procedure, and surgery is saved for more complex cases.

Living with this condition

Most people with a bone cyst live a completely normal life. If the cyst is small and stable, you may only need a check-up X-ray every year or two. If you have had a procedure, you will follow the team's advice about rest, movement, and returning to activity. Avoid heavy lifting or high-impact contact sports until the specialist confirms the bone is strong.

Lifestyle tips

• Stay as active as possible with low-impact activities like swimming or cycling, if allowed.
• Do not stop all movement unless told to — the bone stays healthiest with gentle use.
• Use a brace or crutches if recommended, to take pressure off the affected bone.
• Attend all follow-up appointments so the cyst can be monitored.

Diet and exercise

Eat a balanced diet that includes enough calcium and vitamin D to support bone health — found in dairy products, fortified foods, green leafy vegetables, and sunlight. Exercise helps strengthen bones, but if you have a known cyst, choose low-impact activities and check with your specialist first.

Mental health and emotional wellbeing

It can be worrying to hear that you or your child has a bone cyst, especially if a fracture has happened. You may worry about the future or about keeping a child active without causing harm. These feelings are common. Speak to your GP if anxiety is persistent. For children, simple explanations and normal routines often help them cope well.

Prevention

There is no known way to prevent a bone cyst. They develop during normal bone growth and do not appear to be caused by anything you or your child did or ate. However, you can reduce the risk of a fracture by keeping bones strong with a balanced diet and avoiding falls.

Vaccines

No vaccine prevents bone cysts. Keep other vaccinations up to date to stay generally healthy.

Screening programmes

No routine screening for bone cysts is needed in the general population.

Complications

If left untreated

• Pathological fracture — a break that happens through the weakened bone.
• Growth disturbance in a child if the cyst is near the growth plate.
• Recurrence — the cyst can come back after treatment, especially if it was large.
• Rarely, the cyst may expand and press on nearby structures, causing more pain or mobility problems.

Long-term outlook

The outlook for most bone cysts is very good. Many simple cysts heal on their own or after a straightforward procedure. With proper monitoring and treatment when needed, most children and adults return to normal activities without lasting problems. Even if a cyst recurs, further treatment is usually successful.

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