What is JIA?

Juvenile Idiopathic Arthritis (JIA) is an autoimmune disorder where the body’s natural defences (designed to stop infections) start to attack the joints. This causes to inflammation of the joints, leading to pain, discomfort and reduced mobility.

‘JIA’ means:

Juvenile – the arthritis began before the age of 16. When a young person with JIA turns 16, they still have ‘JIA’ because the condition is different from adult types of arthritis.

Idiopathic – means that the cause is unknown.

Arthritis – means that one or more joints are inflamed, usually for at least six weeks.

Our booklet, My JIA, is a comprehensive guide to living with juvenile idiopathic arthritis (JIA). It is aimed at anyone who has been diagnosed with JIA, as well as their parents, carers and schools and is packed full of information that will help you on your own journey with JIA. To get your copy, click here.



Click here to find out more about Juvenile Arthritis Research.

JIA is usually diagnosed by a specialist paediatric rheumatologist. This is a doctor who is trained in conditions like JIA. At the first assessment, the doctor will check each joint for inflammation and range of movement to see how many joints are affected. Each time you then return to the doctor, they will check the joints again to see how things have changed.

JIA does not only affect the joints. In around 1 in 5 children with JIA, the eyes can also be affected – a condition known as uveitis. If you are diagnosed with JIA, it is very important you get your eyes checked urgently for uveitis as it can lead to permanent sight loss if left untreated. More information about uveitis is available here and support is available from Olivia’s Vision.

There are different types of JIA. Your doctor will tell you which type of JIA you have. You don’t need to know all about the different types, but you might find it helpful to know that there are different types – particularly when you meet other people with JIA. Each person with JIA is affected in a slightly different way. You are unique in every way, including your JIA.

Oligoarticular JIA

Also known as ‘oligo JIA’, this is the most common type of JIA. This is where 4 or fewer joints are affected in the first six months. In some children, it may spread to involve more joints (this is called ‘extended oligo JIA’).

Polyarticular JIA

Also known as ‘poly JIA’, this is where 5 or more joints are affected in the first six months.

Enthesitis-related arthritis

In this form of arthritis, usually called ERA, the inflammation is in the places where the tendons attach to the bone. Children with ERA often suffer pain in the spine and hips.

Psoriatic arthritis

In this type of JIA, children have a skin rash called psoriasis, which looks like a dry scaly rash. They may also have changes to their nails, which looks like pitting.

Systemic onset JIA

Around 1 in 10 children with JIA have systemic onset JIA (also known as SJIA). Children with SJIA usually have a non-contagious fever and rash. Inflammation not only affects the joints, but also other parts of the body including the heart, liver and lungs. Some children with SJIA develop a rare but potentially life-threatening condition known as Macrophage Activation System. SJIA is different to other types of JIA because it is considered ‘autoinflammatory’ rather than autoimmune. This means a different part of the immune defence is involved.

Undifferentiated arthritis

This is where the arthritis does not fit neatly into any of the other categories.



Around 1 in every 1,000 children and young people under the age of 16 have JIA. That is around 15,000 children in the UK alone.

At present, there is no cure for Juvenile Idiopathic Arthritis. All current treatments seek to reduce the symptoms of JIA, but are not a cure. Whilst these treatments have beneficial effects in reducing pain and inflammation, and provide some protection against long-term joint damage, they come with their own side-effects. In around half of all cases, children go into remission. But in the other half, they are confined to taking powerful drugs long-term, with all the side-effects and complications that can cause.

If you would like to know more about JIA, including information about the medications and treatments currently available, you may be interested in The Versus Arthritis Centre for Adolescent Rheumatology, within the University College London GOS Institute of Child Health, University College London Hospital and Great Ormond Street Hospital – visit https://adolescent-rheumatology.uk/. Please remember to speak to your doctor in the first instance if you have any questions about your treatment and medicines.

If you are concerned that a child you know may have JIA, please see our #ThinkJIA resources at www.thinkjia.org

Here at Juvenile Arthritis Research, our vision is a world where no child has to suffer from arthritis. Find out more about us and our aims. If you would like to support our work, click here.