Rheumatoid arthritis - Causes of rheumatoid arthritis

Rheumatoid arthritis is an autoimmune condition, which means it is caused by the body’s immune system attacking itself. However, it is not yet known what triggers this.

Normally, your immune system makes antibodies that attack bacteria and viruses, helping fight infection. But if you have rheumatoid arthritis, your immune system mistakenly sends antibodies to the lining of your joints, where they attack the tissue surrounding the joint.

This causes the thin layer of cells (synovium) covering your joints to become sore and inflamed.

This inflammation in turn causes chemicals to be released that thicken the synovium and damage nearby:

• bones
• cartilage – the stretchy connective tissue between bones
• tendons – the tissue that connects bone to muscle
• ligaments – the tissue that connects bone and cartilage

If the condition is not treated, these chemicals gradually cause the joint to lose its shape and alignment and, eventually, can destroy the joint completely.

Various theories of why the immune system starts to attack the joints have been suggested, including that an infection or virus may trigger this, but none of these theories has been proven.

Possible risk factors

There are a number of things that may increase your risk of developing rheumatoid arthritis, including:

• your genes – there is some evidence that rheumatoid arthritis can run in families, although the risk of inheriting the condition is thought to be low as genes are only thought to play a small role in the condition
• hormones – rheumatoid arthritis is more common in women than men, which may be due to the effects of a hormone called oestrogen that is found at higher levels in women, although this has not been conclusively proven
• smoking – some evidence suggests that people who smoke are at an increased risk of developing rheumatoid arthritis

Want to know more?

• National Rheumatoid Arthritis Society (NRAS): Possible causes and risk factors