Knee osteoarthritis, commonly known as wear-and-tear of the knee, is a condition in which the cartilage, which is the natural cushioning between joints, wears away. This causes the bones of the joints to rub more closely against one another, reducing the shock-absorbing benefits of cartilage. The rubbing results in pain, swelling, stiffness, decreased ability to move, and sometimes, the formation of bone spurs.