Rheumatoid arthritis is an autoimmune disease where your immune system attacks the lining of your joints

Rheumatoid arthritis (RA) happens when your body's immune system mistakenly treats the tissue that lines your joints as a threat and attacks it. This lining, called the synovium, becomes inflamed and swollen. Over time, that inflammation can damage the bone and cartilage inside the joint itself. Unlike osteoarthritis, which comes from wear and tear, RA is your own immune system doing the damage.

The disease usually starts in smaller joints — your fingers, hands, wrists, and toes — and often affects both sides of your body at the same time. You might notice stiffness that is worst in the morning and lasts for hours. The joints may feel warm, look red or puffy, and hurt even when you are not moving them. RA can also cause fatigue, low-grade fever, and a general feeling of being unwell.

RA is not the same as osteoarthritis, the most common type of arthritis. Osteoarthritis comes from the joint wearing down over decades. RA can start at any age, though it most often begins between ages 30 and 60, and it strikes women about three times more often than men.

Key Takeaways

  • Rheumatoid arthritis is caused by your immune system attacking the lining of your joints, not by wear and tear.
  • The disease usually starts in small joints like fingers and wrists and often affects both sides of your body equally.
  • Genetics play a role — certain genes make RA more likely — but having the gene does not mean you will develop the disease.
  • Environmental triggers like smoking, infections, or stress may set up RA in people who are genetically predisposed.
  • Early treatment can slow or stop joint damage, so recognizing symptoms and seeing a doctor matters.

The role of genetics in rheumatoid arthritis

RA runs in families, but not in a straightforward way. If your parent or sibling has RA, your risk is higher than someone with no family history, but you are not may provide to develop it. Researchers have found that certain genes — particularly one called HLA-DR4 — appear more often in people with RA. These genes seem to make your immune system more likely to misfire.

The catch is that many people carry these genes and never get RA. This is why scientists believe genetics loads the gun, but something else pulls the trigger. That something else is likely an environmental factor or a combination of them.

Environmental triggers that may set up rheumatoid arthritis

Smoking is the strongest environmental risk factor linked to RA. People who smoke are two to three times more likely to develop the disease than non-smokers, and smokers tend to have more severe symptoms. Quitting smoking does not erase the risk if you have already developed RA, but it can slow the disease's progress.

Infections may also play a role. Some researchers believe that certain bacterial or viral infections — including Epstein-Barr virus and some gut bacteria — might trigger RA in people whose genes make them vulnerable. The infection itself may pass, but it can leave your immune system in a state where it keeps attacking your joints.

Hormonal changes are another piece of the puzzle. RA is more common in women, and some women notice their symptoms improve during pregnancy (when hormone levels shift) or worsen after giving birth. Hormone replacement therapy and oral contraceptives may also influence risk, though the research is mixed.

Stress and trauma have been reported by many people with RA as triggers, though the scientific evidence is still developing. Physical trauma — a serious injury or surgery — has been linked to RA onset in some cases.

How the immune system goes wrong in rheumatoid arthritis

Normally, your immune system identifies invaders like bacteria and viruses and attacks them. In RA, something breaks down in this system. Your immune cells — particularly B cells and T cells — start treating the synovium (joint lining) as an enemy and release inflammatory chemicals to attack it.

This triggers a cascade: the synovium swells and thickens, more immune cells flood in, and inflammatory molecules like tumor necrosis factor (TNF) and interleukin-6 (IL-6) build up. These molecules are the reason your joints hurt and swell. If the inflammation is not stopped, it spreads deeper into the joint, eroding the cartilage and bone underneath.

This is why early treatment is so important. Modern RA medications work by interrupting this cascade — some block TNF, others block IL-6, and others calm down the B and T cells themselves. The goal is to stop the inflammation before permanent damage happens.

The difference between rheumatoid arthritis and osteoarthritis

Osteoarthritis and RA are both joint diseases, but they start in completely different ways. Osteoarthritis is mechanical — the cartilage that cushions your joints wears down over time from use, age, or injury. It usually affects one side of the body (your left knee, for example) and develops slowly over years. It is most common in people over 65.

RA is inflammatory and autoimmune. It can start suddenly, often affects both sides of your body at once, and can happen at any age. The inflammation is the disease itself, not a side effect of wear and tear. This is why the treatments are different: osteoarthritis is often managed with pain relief and joint protection, while RA requires medications that calm the immune system.

You can have both conditions at the same time, but they are separate diseases with separate causes.

Symptoms that suggest rheumatoid arthritis rather than other conditions

RA has a recognizable pattern that can help you and your doctor spot it early. Morning stiffness lasting more than an hour is a classic sign — with osteoarthritis, stiffness usually eases within 15 to 30 minutes. Symmetrical swelling (both hands, both wrists, both feet) is another red flag for RA.

Other symptoms include joint pain that does not improve with rest, warmth or redness around the joints, fatigue that does not match your activity level, and sometimes a low fever or loss of appetite. Some people develop rheumatoid nodules — firm lumps under the skin, usually on the elbows or fingers.

A blood test can check for two markers: rheumatoid factor (RF) and anti-CCP antibodies. Many people with RA have one or both of these in their blood, though not everyone does. An X-ray or ultrasound can show whether joints have been damaged. If you notice these symptoms, seeing a rheumatologist (a doctor who specializes in joint and autoimmune diseases) is the next step.

Why early diagnosis and treatment matter for rheumatoid arthritis

The first few months after RA starts are critical. During this window, inflammation can cause permanent damage to bone and cartilage that cannot be reversed. This is why rheumatologists push for early, aggressive treatment — not to be harsh, but because it works. Studies show that people treated early have less joint damage and better long-term outcomes than those who wait.

Modern RA medications have changed the disease dramatically. Decades ago, RA often led to severe disability. Today, many people with RA who start treatment early go into remission or low-disease activity, meaning their symptoms quiet down and their joints stay protected. This is not a cure, but it is a very different picture from what older treatments could offer.

If you think you might have RA, the step is to see your primary care doctor or ask for a referral to a rheumatologist. Bring a list of which joints hurt, when the pain started, how long morning stiffness lasts, and whether anyone in your family has RA or other autoimmune diseases. This information helps the doctor narrow down the diagnosis.

Frequently Asked Questions

Can you catch rheumatoid arthritis from someone else?

No. RA is not contagious. It is an autoimmune disease that develops in your own body when your immune system misfires. You cannot catch it from another person, and you cannot pass it to someone else.

Does rheumatoid arthritis run in families?

RA does run in families, but it is not may provide. If a parent or sibling has RA, your risk is higher than average. However, many people with a family history never develop RA, and many people without any family history do develop it. Genes are part of the picture, but not the whole story.

Can you get rheumatoid arthritis from an injury?

An injury alone does not cause RA, but some people notice RA symptoms starting after a serious injury or surgery. Researchers think the trauma may trigger the disease in people who are already genetically predisposed. If you have a family history of RA and develop joint symptoms after an injury, mention this to your doctor.

Is rheumatoid arthritis worse in cold weather?

Many people with RA report that their symptoms worsen in cold, damp weather, though the scientific reason is not fully understood. It may be related to changes in barometric pressure or to people moving less in cold weather. Keeping joints warm and staying active can help manage symptoms year-round.

What is the difference between rheumatoid factor positive and negative?

Rheumatoid factor (RF) is an antibody that appears in the blood of about 80 percent of people with RA. If your RF test is positive, it supports an RA diagnosis. If it is negative, you might still have RA — about 20 percent of people with RA are RF-negative. Your doctor will look at your symptoms, imaging, and other blood tests to confirm the diagnosis either way.