Osteoarthritis (OA) is the most frequent cause of disability among adults in the developed world. Arthritis affects around 15% in Australia (3 million people). More than 20 million people in the United States have the disease. The lifetime risk of knee OA for males and females aged over 45 years is between 45% (nonobese) to 70% for obese. The cost in USA is more than $60 billion per year.It is second only to ischemic heart disease as a cause of work disability for men over 50 years.