Inflammatory arthritis is caused by swelling and tenderness inside the tough layer of tissue that forms a protective capsule around the joint. The synovial membrane usually helps to lubricate the joint, but when it becomes inflamed it can stop the joint from working well. This inflammation can also damage the cartilage and bone. It is important to try and treat the inflammation at an early stage.

The most common type of inflammatory arthritis is rheumatoid arthritis. Other types include ankylosing spondylitis, gout, reactive arthritis, arthritis associated with psoriasis and systemic lupus erythematosus (SLE).

Rheumatoid arthritis is caused by the body's normal defence system going into action against the soft tissue within joints. Inflammation is helpful when there is an infection to fight as it is a way of getting our defensive chemicals to the right place. However it is not helpful for joints when there is no infection to fight. It's not clear why this reaction happens.

Rheumatoid arthritis can affect people at any age, but it most commonly develops between the ages of 30 and 50. Women are three times more likely to develop it than men.

For four out of five people with rheumatoid arthritis the condition develops slowly over several months. For other people it can develop very rapidly. The inflammation tends to go in cycles and the amount of damage that is caused to the joints varies from person to person. It is important to treat the inflammation as quickly as possible to try and prevent long-term damage.