When you are told that your child has arthritis you will probably have mixed feelings. You may feel angry or confused, wanting to know why your child should have an illness which most people think only happens to older people. You may also feel relieved that at last somebody has put a name to the illness your child has been suffering from for weeks or months and finally treatment can begin. Whatever you feel, you will probably have a lot of questions. Juvenile arthritis (JA), or 'juvenile idiopathic arthritis' to give it its official title, is really a group of illnesses which doctors have put under one name because they share similar symptoms. It simply refers to arthritis with no known cause in children or young people under the age of 16.