These membranes get inflamed, resulting in synovitis, causing pain, along with swelling. If left unchecked, the disease progresses and causes a destruction of bones, cartilages, and ligaments, leading to disability. Almost 1% of the world population and about 1.3 million Americans are affected by this disease. The onset occurs mostly between the age of forty and sixty. Women are three times more likely to be affected by this disease. It often runs in families and may point towards a genetic predisposition.