Rheumatoid arthritis develops when your immune system mistakenly attacks the lining of your joints

Rheumatoid arthritis (RA) is not caused by wear and tear or injury. Instead, your body's immune system becomes confused and treats the tissue that lines your joints — called the synovium — as a threat. This triggers inflammation that damages the joint lining, cartilage, and eventually bone. The result is pain, swelling, stiffness, and loss of movement, usually in the hands, wrists, feet, and knees.

Unlike osteoarthritis, which develops gradually over years as joints wear down, RA can develop quickly and affect multiple joints at the same time. It is also a systemic disease, meaning it can affect other parts of your body beyond your joints — including your heart, lungs, eyes, and skin.

Key Takeaways

  • Rheumatoid arthritis happens when your immune system attacks joint linings, not because of age, activity level, or past injury.
  • Genetics play a role — certain genes make RA more likely, but having the gene does not may provide you will develop the disease.
  • Environmental triggers such as smoking, infections, or stress may set up RA in people who are genetically predisposed.
  • RA typically appears between ages 30 and 60, though it can develop at any age, including in children.
  • Early diagnosis and treatment can slow or stop joint damage, which is why recognizing early symptoms matters.

The role of genetics in developing rheumatoid arthritis

If a parent or sibling has RA, your risk is higher than the general population. Researchers have identified specific genes — particularly one called HLA-DR4 — that are more common in people with RA. However, having these genes does not mean you will develop the disease. Many people carry RA-related genes and never develop symptoms.

Genetics loads the gun, but something else pulls the trigger. That something is usually an environmental factor or a combination of factors. This is why identical twins, who share 100 percent of their DNA, do not always both develop RA — one may develop it and the other may not.

Environmental triggers that may set up rheumatoid arthritis

Smoking is the strongest environmental risk factor identified so far. People who smoke are two to three times more likely to develop RA than non-smokers, and the risk increases with how much and how long someone smokes. Even former smokers have elevated risk for years after quitting, though the risk does decline over time.

Infections may also play a role. Researchers have found that certain bacterial and viral infections — including the Epstein-Barr virus and some gut bacteria — may trigger RA in genetically vulnerable people. The infection itself may pass, but the immune system response it sets off can persist and lead to RA.

Hormonal changes, particularly in women, may contribute as well. RA is two to three times more common in women than men, and some women notice symptoms beginning or worsening after pregnancy or during menopause. Oral contraceptives may lower risk, though the relationship is complex and not fully understood.

Why women develop rheumatoid arthritis more often than men

The female hormone estrogen appears to influence immune function in ways that increase RA risk. Women's immune systems are naturally more active than men's, which provides some protection against infection but also makes autoimmune diseases more likely. This is why women are more prone to RA, lupus, and other autoimmune conditions.

Pregnancy itself is interesting: many women experience temporary improvement during pregnancy because of hormonal and immune changes, but symptoms often return or worsen after delivery. This pattern suggests that hormonal shifts, not just the presence of female hormones, matter in RA development.

Age and the timing of rheumatoid arthritis onset

RA most commonly appears between ages 30 and 60, with peak onset in the 40s and 50s. However, it can develop at any age. Juvenile idiopathic arthritis (JIA) affects children, and RA can appear in people in their 20s or in their 70s and 80s.

The reason RA typically emerges in middle age is not fully clear. It may take years of immune system dysregulation before enough joint damage accumulates to cause noticeable symptoms. Alternatively, the combination of genetic predisposition and accumulated environmental exposures may straightforward reach a tipping point by midlife.

Stress and other lifestyle factors

Chronic stress may increase RA risk or trigger flares in people who already have the disease. Stress hormones affect immune function, and prolonged stress can shift the immune system toward inflammation. This does not mean stress causes RA on its own, but in someone genetically predisposed, stress may be part of the trigger.

Obesity is also associated with higher RA risk, particularly in women. Excess body fat produces inflammatory chemicals that may set up or worsen autoimmune responses. Weight loss has been shown to reduce RA symptoms in some people, though it does not reverse existing joint damage.

Diet, sleep, and physical activity all influence inflammation levels in the body. While no food or lifestyle change can prevent RA in someone destined to develop it, these factors may affect how severe symptoms become or how quickly the disease progresses.

What you cannot catch or inherit automatically

RA is not contagious. You cannot catch it from someone who has it, even with prolonged close contact. It is also not purely inherited — having a parent with RA does not mean you will develop it. Instead, RA requires a combination of genetic susceptibility and environmental triggers that vary from person to person.

This is why two siblings with the same parents may have very different outcomes: one may develop RA while the other never does, depending on their individual genetics, exposures, and life circumstances.

Frequently Asked Questions

Can you get rheumatoid arthritis from an injury or overuse?

No. Injury or overuse can cause joint pain and inflammation, but they do not cause RA. RA is an autoimmune disease that develops when your immune system attacks joint linings. An injury might make an existing RA joint feel worse, but it does not trigger RA itself.

If I have the genes for rheumatoid arthritis, will I definitely get it?

No. Many people carry RA-related genes and never develop the disease. Genes increase your risk, but an environmental trigger — such as smoking, infection, or stress — is usually needed to set up RA. Without that trigger, the genes alone are not enough.

Does rheumatoid arthritis run in families?

RA does tend to cluster in families because of shared genes, but it is not may provide to pass from parent to child. If a parent has RA, your risk is higher than average, but most children of people with RA do not develop it. Environmental factors and individual genetics matter as much as family history.

Can you develop rheumatoid arthritis at any age?

Yes, though it is most common between ages 30 and 60. Children can develop juvenile idiopathic arthritis, and RA can appear in people in their 20s or much later in life. If you notice joint pain, swelling, or stiffness that lasts more than a few weeks, it is worth discussing with a doctor regardless of your age.

Does smoking definitely cause rheumatoid arthritis?

Smoking significantly increases RA risk, especially in people who are genetically predisposed, but it does not may provide you will develop RA. Some smokers never develop it, while some non-smokers do. Smoking is the strongest modifiable risk factor, meaning quitting is one of the few things you can control to lower your risk.