by Jodeann Cooley, PTA Osteoarthritis is commonly known as wear and tear arthritis. OA is the most common type of arthritis. More than 27 million people in the U.S. have OA, and knees are the most commonly affected area. Osteoarthritis is caused when the natural cushioning between joints (cartilage) wears away. This causes the bones of the knee to rub… Read more