Most of us think of arthritis as something that afflicts older people but juvenile arthritis is one of the most common childhood diseases in the U.S. , affecting nearly 300,000 children. One of those is 10-year-old Synnove Solberg of Edmonds, who was diagnosed with Polyarticular Rheumatoid Arthritis when she was 6. According to her mom, Carol Solberg, “polyarticular” means “many joints,” and Synnove…