Skip to main content

Alert COVID-19

Please find service updates and current visiting rules in our COVID-19 section.

This site is best viewed with a modern browser. You appear to be using an old version of Internet Explorer.

What's happening to me?

This page explains some of the background to JIA, other inflammation and pain.

For information on a specific condition, check out our A-Z of conditions.

What is inflammation?

Inflammation is the process that underlies JIA and all other inflammatory conditions. It is also what happens during an infection, following a bee sting, when an allergy occurs or when the body responds to trauma such as a cut or a broken arm.

Inflammation is the body's response to something it recognises as being harmful. It wants to remove the harmful agent and any damage, then begin to repair itself.

To do this, it increases blood supply to the affected area and white cells and fluid from the blood move into the tissues. This explains, in part, why inflammation of the skin is hot and swollen.

The white blood cells are part of the immune system, designed to protect the body against infection caused by bacteria and viruses (also known as germs). These cells circulate in the blood and do most of the work to release chemicals to destroy the harmful agent and break down damaged tissue. These chemicals irritate nearby nerves and other cells causing pain.

Rashes, mouth ulcers, bone and joint swelling, red eyes, sore throats, coughs and  tender muscles are caused by the same underlying process.

A normal knee joint with the right amount of fluidWhat is an inflammatory or rheumatological disease?

In an inflammatory condition, the immune system mistakenly attacks a part or parts of the body as it would if they were infected. This causes an increase in blood supply, swelling and sometimes pain.

JIA is this inflammation in the joints. In JIA the immune system attacks the lining of the joint making it produce excess joint fluid which makes the joint swollen and painful. Stiffness is caused by swelling of the joint lining and chemicals released by the white cells in the joint.

When the immune system acts against the body by mistake it is called autoimmunity.

A sore, swollen knee joint of an arthritis suffererIs inflammation responsible for all pain?

No. Pain may be caused by damage to nerves and tissues from wear and tear or from trauma. Pain may also be felt when the pain system has gone wrong and is not giving reliable information.

See pain management for more information on what causes pain and what you can do to reduce it.

Why do I have an inflammatory disease?

Bad luck is probably the best explanation. However, we know that some people have a risk factor in their genes, which is only important if it is triggered by something in the environment (perhaps an infection or allergy). Many people have the risk factor, but do not get an inflammatory disease.