Arthritis is a common condition that causes pain and inflammation (swelling) of the joints and bones. The main symptoms of arthritis include:
- restricted movements of the joints
- inflammation and swelling
- warmth and redness of the skin over the joint
In the UK, arthritis is a very common condition, affecting over nine million people.
The most common forms of arthritis are:
- rheumatoid arthritis
The characteristics of these two conditions are discussed below. Other types of arthritis are listed in the box, below left.
What is osteoarthritis?
Osteoarthritis is the most common form of arthritis in the UK, affecting an estimated 8.5 million people.
In people affected by osteoarthritis, the cartilage (connective tissue) between their bones gradually wastes away (degenerates), leading to painful rubbing of bone on bone in the joints. The most frequently affected joints are in the:
Osteoarthritis often develops in people who are over 50 years of age. However, it can develop at any age as a result of an injury or another joint-related condition.
The cause of osteoarthritis is not fully understood. One theory is that some people are genetically predisposed to developing osteoarthritis, which means that they have an increased likelihood of inheriting it from their parents. However, this theory has not yet been proven.
What is rheumatoid arthritis?
Rheumatoid arthritis is a more severe, but less common, form of arthritis than osteoarthritis. It occurs when the body's immune system attacks and destroys the affected joints, causing pain and swelling to occur. This can lead to a reduction in movement and the breakdown of bone and cartilage.
In the UK, rheumatoid arthritis affects around 350,000 people, and it often starts between 40 and 50 years of age. Women are three times more likely to be affected by the condition than men.
Rheumatoid arthritis is caused by a fault in the immune system (the body’s natural defence against illness and infection) that makes the body attack its own tissues. The fault may be inherited genetically (passed on from a family member).