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Children and young people having an injection into a joint under Entonox

Patient information A-Z

This leaflet is a guide to your child or young person coming to Cambridge University Hospitals at Addenbrooke’s for a steroid joint injection under Entonox.

Having Entonox (gas and air)

If you, the patient and your doctor all agree, they can be offered a joint injection with Entonox, sometimes called gas and air or ‘laughing gas’. Entonox works by making the patient feel relaxed and sometimes giggly, to provide pain relief whilst having the joint injection(s). Entonox is breathed in through a tube placed between the lips and held by the patient.

The patient will have numbing cream or spray applied to the skin over the joint(s) to be injected and they can be supported by a member of the play team or nursing staff whilst the procedure takes place, either in clinic or on a ward. Parents are welcome to be present throughout. The child or young person will be encouraged to practise with the gas and air before the procedure begins and will be able to tell the team giving the injection when they are ready to proceed.

The injection

If your child or young person has joints affected by arthritis, this may be treated with an injection of steroid medication known as a ‘corticosteroid’, given directly into the painful swollen joint. This is beneficial because:

  • Steroids reduce pain and swelling caused by arthritis.
  • Excess fluid around the joint can be removed at the same time, where possible.
  • Giving the steroids directly into the joint reduces the risk of generalised side effects.
  • The injection works quickly to make the joint more comfortable.
  • Results can last for months or often longer.
  • If the effects of the injection wear off, it can be repeated if your doctor advises that this is appropriate. There may be a minimum time period of three months before the next injection can be given.

Some injections require X-ray guidance to ensure the correct placement of the medication into the joint. If this is the case, this will be explained to you prior to the procedure.

Please watch What? Why? Children in Hospital's video (opens in a new tab) with your child or young person, which shows how the joint injection under Entonox is done.

After the injection

  • It is important your child rests for 24 hours. After this time they can return to normal activities. You will need to acquire a wheelchair (unless your child uses a pushchair) on your way into the hospital / before you leave as they must not walk immediately following the procedure.
  • Your child might require simple pain relief for the first 48 hours.

Side effects

Possible side effects of the injectable corticosteroid include:

  • Risk of infection inside the joint. This is a very small risk and the health professional performing the procedure will take every care to use sterile (clean) techniques. See ‘When to seek medical attention’ section below.
  • Thinning of the fat layer under the skin over the joint injection site can occur. This may result in an appearance like a small scar which can emerge a few months after the procedure.
  • Steroids injected into joints can sometimes be seen as deposits on X-rays. This does not cause pain or affect the function of the joint.

When to seek medical attention

Monitor the child or young person closely for 24 to 48 hours after the joint injection. If they suffer a high temperature (fever), redness to the area, or pain which is getting worse over the injection site and / or around the injected joints, seek immediate medical advice. If this is out of hours, please contact NHS 111 (opens in a new tab).

If you have any questions or concerns, please contact the Paediatric Rheumatology advice line between 8am and 4pm Monday to Friday on 01223 254988 or email paediatric rheumatology.

We are smoke-free

Smoking is not allowed anywhere on the hospital campus. For advice and support in quitting, contact your GP or the free NHS stop smoking helpline on 0800 169 0 169.

Other formats

Help accessing this information in other formats is available. To find out more about the services we provide, please visit our patient information help page (see link below) or telephone 01223 256998.

Contact us

Cambridge University Hospitals
NHS Foundation Trust
Hills Road, Cambridge

Telephone +44 (0)1223 245151