 Hi, I'm Dr. Sunil Kini working as a concert and orthopedic surgeon at Manipal Hospital's Bangalore. The onset age for arthritis depends on what condition we are treating. The most common osteoarthritis or age-related arthritis occurs in the elderly population. Other forms of arthritis such as inflammatory arthritis occurs in the middle age or the young population. And some forms of arthritis such as bacterial and viral arthritis, gouty arthritis, usually involves the younger population, although it is not a matter of rule.