Arthritis is joint inflammation. This joint inflammation causes swelling, pain and stiffness. If the disease lasts long or occurs repeatedly, it can lead to tissue damage. Arthritis is not always limited to the joints of the body and can affect soft tissues and internal organs.
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.