In the joint, inflammation causes damage to the cartilage and synovial lining. When the cartilage is warn down, the space in the joint becomes smaller and the bones may rub together. Damage to the synovial lining cause synovial fluid to leak and produce fluid in the joint lining. This adds to the swelling along with the inflammatory response of the body. If the joint lining continues to grow, it can permanently damage the bone. All of this causes pain, swelling and distress for the patient.