Cartilage is a firm but flexible connective tissue in your joints. It protects the joints by absorbing the pressure and shock created when you move and put stress on them. A reduction in the normal amount of this cartilage tissue cause some forms of arthritis.

Normal wear and tear causes OA, one of the most common forms of arthritis. An infection or injury to the joints can exacerbate this natural breakdown of cartilage tissue. Your risk of developing OA may be higher if you have a family history of the disease.

Another common form of arthritis, RA, is an autoimmune disorder. It occurs when your body’s immune system attacks the tissues of the body. These attacks affect the synovium, a soft tissue in your joints that produces a fluid that nourishes the cartilage and lubricates the joints.

RA is a disease of the synovium that will invade and destroy a joint. It can eventually lead to the destruction of both bone and cartilage inside the joint.

The exact cause of the immune system’s attacks is unknown. But scientists have discovered genetic markers that increase your risk of developing RA fivefold.