One third of our population will have arthritis at some time in their lives and the number is steadily increasing as the population ages. Fortunately, we now have a better understanding than ever before of how arthritis causes damage and how damage can be prevented. Indeed over the past 20 years there has been a revolution that is likely to continue, revealing newer, safer and more effective methods of prevention and treatment.

How joints work

In order to have an understanding of the two major types of arthritis, it is essential to know a little about the function and appearance of a joint. A joint is designed to allow smooth movement of two bones, one against the other.

Essential components of the joint are:

Ligaments - ‘rope-like’ bands that holds the bones together

Cartilage - smooth material that allows one bone to move over the other without friction

Synovium - the joint lining cells that produce a small amount of fluid (like oil) to lubricate the joint.

Tendons - strong bands of fibre that attach a muscle to a bone. They are less elastic than muscles themselves.

The types of arthritis

Osteoarthritis (or degenerative arthritis) is the most common form. It occurs when the cartilage of the joint gradually wears away, exposing bare bones that rub against one another. This makes the joints stiff ‘creaky’ and painful. As this disease is a ‘wear and tear’ disease, it tends to occur in older people and in those whose joints have been damaged by injury.

Rheumatoid arthritis, on the other hand, is an ‘inflammatory arthritis’. The synovium becomes much thicker and changes in character so that the inflammatory cells within it start to eat away at everything they touch.

Joints affected by rheumatoid arthritis often become unstable and slip out of place, causing deformities of the hand, for example. It commonly affects younger women aged 20 - 50 years.