What is JIA?

JIA stands for Juvenile Idiopathic Arthritis.

  • Juvenile: It affects children and adolescents under the age of 16.
  • Idiopathic: It has no known cause.
  • Arthritis: It is a chronic (long-lasting) inflammation of the joints.

JIA may be most simply defined as a long-term inflammatory disorder of the joints affecting under-16s that has no obvious cause. There are seven main types of JIA.


JIA – A Medical Description (PDF)


How common is it?

JIA affects approximately one out of every 1,000 people under the age of 16.

How is it diagnosed?

Many children and adolescents occasionally find that they have swollen, painful joints. Often this is due to some obvious cause, such a recent injury or an infection. In such cases, your doctor would not normally consider JIA.

On the other hand:

  1. if a child appears to have joints that are swollen, painful, and—especially in the morning or after periods of inactivity—stiff;
  2. if the symptoms persist for at least six weeks; and
  3. if there is no obvious cause for the symptoms

then your doctor may consider a diagnosis of JIA.

It is important to know that is no single diagnostic test for JIA. The condition is identified on the basis of a clinical assessment and a discussion of the patient’s history. Medical staff may, however, carry out a variety of tests in order to exclude other possible causes of a child’s symptoms.