Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Juvenile Arthritis ?
    ### Response:
    Juvenile arthritis (JA) is arthritis that happens in children. It causes joint swelling, pain, stiffness, and loss of motion. It can affect any joint, but is more common in the knees, hands, and feet. In some cases it can affect internal organs as well.    The most common type of JA that children get is juvenile idiopathic arthritis.
    