Many bone cysts will eventually heal without treatment and won't cause any permanent problems.

This is particularly true of unicameral bone cysts in children, which will usually disappear around the time they finish growing.

However, treatment is sometimes necessary if the cyst is painful or is at risk of causing a fracture.

If a cyst has already caused a fracture, this will need to be dealt with before the cyst is treated – usually with painkillers, rest and a plaster cast.

Unicameral bone cysts

If the cyst is small and the affected bone is strong, you or your child may not receive any immediate treatment, but will be given regular check-ups to make sure the cyst is not getting bigger.

Surgical treatment may be recommended if the cyst does not show any signs of healing or if the bone is thought to have a high risk of fracture. There are three main types of surgical treatment:

• steroid injections – where fluid is drained out of the cyst before steroid medication is injected into it; several injections may be required a few months apart to help ensure the cyst fully heals
• bone marrow injections – similar to steroid injections, but the surgeon injects bone marrow that has been removed from another part of the body to encourage the cyst to heal
• curettage and bone grafting – where the surgeon cuts into the bone, drains the cyst, and scrapes out the lining of the cyst; the resulting hole is then usually filled with chips of bone from another part of the body or a donor

All three techniques are carried out under general anaesthetic, which means that you or your child will be asleep during the surgery and will not feel any pain. Most people can go home later the same day, although you may need to take things easy for a few months while you recover.

In some cases, unicameral bone cysts can return after treatment, usually within a year or two. Therefore, it's likely that you or your child will have regular X-rays to assess the condition of the affected bone and check for signs of the cyst recurring.

Aneurysmal bone cysts

Aneurysmal bone cysts usually need to be treated because they don't tend to get better on their own and they can get bigger rapidly. In many cases, simple treatment such as carrying out a biopsy of the cyst will start the healing process.

If this does not work, they are treated using curettage and sometimes with bone grafting, as described above.

In some cases, additional treatments such as a procedure to block the blood supply to the blood vessels near the cyst (embolisation) or to freeze and damage the tissue of the cyst using liquid nitrogen may also be carried out.

Like unicameral bone cysts, aneurysmal bone cysts may sometimes come back after treatment. This usually happens within 18 months, if it’s going to.