RHEUMATOID ARTHRITIS DEFINITION

Arthritis affects approximately 500,000 Irish men and women and over 5,000 Irish children under the age of 12. There are over 100 types of arthritis.

Rheumatoid arthritis (RA) is a chronic, auto-immune, inflammatory disease mainly affecting the joints. It affects approximately 1 percent of the Irish adult population, over 80 percent of whom develop the disease between the ages of 35 and 50. RA is significantly more prevalent in women than in men, with the overall ratio about three women to one man.

To understand how RA affects the joints, it is helpful to know how a normal joint works. Put simply, a joint is where two bones meet. To allow the bones to move against each other without friction, each bone is covered with cartilage, which has a smooth slippery surface. The joint is surrounded by a membrane (the synovium). The synovium produces a thick fluid called synovial fluid, which acts as a lubricant to help the joints move smoothly.

In RA the synovial membrane of the joints is persistently inflammed. Inflammation is a normal response produced by the body’s immune system to fight off infection and heal injury. The inflammatory reaction is self-limiting and works to the benefit of the body.

In RA the inflammation in the synovial membrane does not subside in the normal manner, instead it persists. The synovial membrane becomes thickened and protrudes into the joint resulting in destruction of the cartilage and erosion of bone. This inflammation process may eventually result in the joint becoming deformed. The muscles, ligaments and other soft tissue around the joint are also weakened. Combined with the deformity, this reduces the function of the joint.

RA is a multi-system or systemic disease, meaning it can affect the all of the body systems.