Rheumatoid arthritis is one of the most common forms of arthritis. One percent of the world's population suffers from it.
The term actually refers to a family of related diseases where the main characteristic is the persistent inflammation of the membrane lining of the joint, called the synovium.
Any joint with a synovial membrane can develop the disease. In general, it starts in the joints of the hands or feet, with those in the middle and at the base of the fingers being most frequently affected, followed by the wrist, knees, ankles, elbows and hips.
The process of inflammation is how the body reacts to damage, or the presence of a foreign substance. Ordinarily this is a good thing, helping the body to fight infection and recover. The body increases the blood flow to the damaged/infected site to deliver white blood cells to fight the infection, causing the area to become inflamed.
Normally the inflammatory process is self-limited and tightly controlled. But in rheumatoid arthritis, the body for some reason believes that there is persistent damage/ foreign substance in the joint in question and acts accordingly,
The increased blood flow to the joint causes it to become red and hot (inflamed). This enhanced blood supply also means more nourishment for the synovium, leading to thickening of the synovium and the overproduction of synovial fluid. This causes the joint to become swollen and puffy, narrowing the joint space.
As the disease progresses, the synovial cells begin to invade and destroy the cartilage within the joint. The cartilage becomes rough and pitted instead of smooth and slippery, making movement difficult and uncomfortable. The bone of the joint becomes damaged. The surrounding muscles, ligaments and tendons that support the joint become weak and unable to work normally and the tendons may even rupture due to the swollen tissue.
The involved joint can eventually lose its alignment, causing pain, reduced movement and loss of function.
The joints of the hand often appear most affected - they can be so badly damaged that fine movements are limited. Destruction of the joint can lead to the wrist turning towards the thumb side of the hand, causing what is known as ulnar drift of the fingers.
The inflammatory process can also affect other parts of the body to cause anaemia, breathlessness, weight loss and flu-like symptoms; it can also affect the nerves, the heart and the lungs. Inflammation of the blood vessels in the eye can occur - a condition called scleritis.
Written by Dr. Anna Tilley
24/04/2009