Rheumatoid arthritis (RA) is a chronic autoimmune disease in which the immune system mistakenly attacks the lining of the joints, causing pain, swelling, and stiffness that can eventually destroy cartilage and bone. It affects roughly three times as many women as men and, unlike the wear-and-tear damage of osteoarthritis, it stems from inflammation that can also harm organs like the heart and lungs.
How RA Differs From Other Arthritis
The hallmark of rheumatoid arthritis is that it’s driven by the immune system, not by mechanical wear on joints. In a healthy joint, a thin membrane called the synovium produces fluid that keeps things lubricated. In RA, immune cells flood that membrane and trigger a cycle of inflammation that doesn’t resolve on its own. The swollen synovium thickens and begins invading the surrounding cartilage and bone.
One practical way to tell the difference early on is morning stiffness. In osteoarthritis, stiffness after waking typically fades within 30 minutes. In RA, it often lasts much longer, sometimes an hour or more, and improves only gradually with movement. RA also tends to be symmetrical: if one wrist or set of knuckles is affected, the same joints on the other hand usually are too.
Common Symptoms
RA typically starts in smaller joints, especially the fingers, wrists, and toes. You may notice swelling, warmth, and tenderness in those joints along with that prolonged morning stiffness. Fatigue is extremely common and often underestimated. Many people describe a deep, persistent tiredness that goes beyond normal sleepiness.
As the disease progresses, it can spread to larger joints like the knees, shoulders, elbows, and ankles. Over time, chronic inflammation can loosen tendons and ligaments, causing joints to shift out of alignment. Some people develop small, firm lumps under the skin near affected joints, called rheumatoid nodules.
What Causes It
RA develops from a combination of genetic susceptibility and environmental triggers. No single gene causes it, but a group of gene variants in a region called HLA-DRB1 accounts for up to 40% of genetic risk. These variants affect how your immune system distinguishes your own tissue from foreign invaders, and they’re most strongly linked to a specific subtype of RA marked by certain antibodies in the blood.
Among environmental triggers, smoking is the most firmly established. Studies estimate it accounts for 20 to 30% of the environmental risk, and it’s especially dangerous for people who carry those high-risk gene variants. Smoking appears to cause chemical changes in proteins at mucosal surfaces like the lungs, which in genetically predisposed people can trigger the immune system to produce the antibodies that drive RA.
The gut microbiome is another area of growing interest. People with early RA show differences in the types and diversity of bacteria in their digestive tract compared to healthy individuals. Specific bacteria, including Prevotella species, have been found at higher levels in fecal samples from people with early disease. The working theory is that at some point before joint symptoms appear, interactions between microbes and the immune system at mucosal surfaces (the gut, mouth, or lungs) break the body’s tolerance for its own tissue.
How RA Is Diagnosed
There’s no single test that confirms RA. Doctors use a combination of physical examination, blood work, and sometimes imaging to piece together a diagnosis. The formal classification system scores four areas on a scale of 0 to 10: how many joints are swollen or tender, whether specific antibodies are present in the blood, whether markers of inflammation are elevated, and whether symptoms have lasted six weeks or longer. A score of 6 or higher points to RA.
Two blood tests play a central role. Rheumatoid factor (RF) has been used for decades but produces false positives fairly often, with a specificity around 85%, meaning 15% of people who test positive don’t actually have RA. A newer test for anti-CCP antibodies is more precise, with specificity between 95 and 96%. Neither test catches everyone, though. Their sensitivity ranges from about 53 to 71%, so a negative result doesn’t rule the disease out. Some people with clear clinical RA never test positive for either antibody.
What Happens Inside the Joints
The damage in RA follows a specific sequence. First, immune cells, particularly a type of white blood cell called macrophages, flood the synovial membrane. Cells lining the membrane begin multiplying rapidly, forming a thickened mass of tissue. This overgrown tissue releases enzymes that break down collagen, the structural protein in cartilage. As cartilage erodes, the joint loses its cushioning and normal range of motion.
Bone loss follows a different pathway. The inflammatory environment activates cells called osteoclasts, which are specialized bone-dissolving cells. At the same time, the cells responsible for building new bone (osteoblasts) are suppressed. The result is erosion that shows up on X-rays as gaps or pits at the edges of joints. This bone damage is largely irreversible, which is why early treatment matters so much.
Effects Beyond the Joints
RA is a systemic disease, meaning the same inflammation that damages joints can affect other parts of the body. The cardiovascular system is one of the most important targets. Women with RA have twice the risk of heart attack compared to women without the disease, and for those who’ve had RA for 10 years or more, the risk triples. Chronic inflammation stiffens artery walls and accelerates the buildup of plaque, even in people without traditional heart disease risk factors.
Lung involvement is more common than many people realize. Autopsy studies have found signs of inflammation in the tissue surrounding the lungs in about half of RA patients, though only about 10% ever develop noticeable symptoms. Some people develop scarring of the lung tissue (pulmonary fibrosis), which tends to occur in men with long-standing disease. Others may develop fluid around the lungs without obvious symptoms.
Dry eyes affect at least 10% of people with RA, often as part of a secondary condition that also causes dry mouth. More serious eye complications, such as deep inflammation of the white of the eye, are rarer but can threaten vision if untreated. Inflammation of the pericardium (the sac around the heart) is another common finding on autopsy that rarely causes noticeable symptoms during life.
Treatment Approach
The standard strategy for RA is called “treat to target,” meaning medications are adjusted with a clear goal: getting the disease into remission or as close to it as possible. In clinical studies, this approach achieved remission in about 64% of patients within two years, compared to roughly 35% with less structured care. The key is starting treatment early and adjusting it aggressively rather than waiting to see how things unfold.
The first medication most people start is methotrexate, taken once a week in pill form. It works by broadly dampening the overactive immune response. Most people tolerate it well, though it requires periodic blood tests to monitor liver function. It remains the backbone of RA treatment and is often the drug other medications are added to.
When methotrexate alone isn’t enough, doctors add a second class of drug. Biologic medications are given by injection or infusion and target specific parts of the immune system. Some block a protein called TNF that drives inflammation; others target different immune pathways. A newer option, JAK inhibitors, works through a different mechanism and comes in pill form, which some people prefer over injections. Both biologics and JAK inhibitors have transformed outcomes for people with moderate to severe RA, making sustained remission a realistic goal for many patients.
Living With RA Long-Term
With modern treatment, many people with RA live active, full lives. The disease course varies widely. Some people achieve remission within the first year and stay there; others cycle through periods of higher and lower disease activity. Physical activity, particularly low-impact exercise like swimming, walking, and strength training, helps maintain joint flexibility and muscle support around affected joints.
Because of the increased cardiovascular risk, managing heart health is an important part of long-term RA care. Controlling inflammation with disease-modifying medications doesn’t just protect joints; it also appears to reduce the excess cardiovascular risk that comes with chronic systemic inflammation. Paying attention to blood pressure, cholesterol, and not smoking matters even more for people with RA than for the general population.