This is what happens when joints — the places where bones meet — get painful, swollen, and stiff. Someone with arthritis may find it painful to move his joints. Arthritis may occur when a person has lost some of the flexible cushion between the bones called cartilage. You may know some older people with the condition. Kids who have arthritis may have an infection, Lyme disease, lupus, or juvenile rheumatoid arthritis.
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