Rheumatoid arthritis (RA) is an autoimmune disease in which your immune system mistakenly attacks the lining of your joints, causing chronic inflammation, pain, and eventually joint damage. Unlike the wear-and-tear arthritis most people think of, RA is driven by immune dysfunction and can affect your entire body. As of 2019, roughly 18 million people worldwide were living with it, and about 70% of them are women.
How RA Differs From Osteoarthritis
Most people who search for “RA arthritis” are trying to understand how it’s different from the more common type of arthritis, osteoarthritis (OA). The differences are fundamental. OA comes from cartilage breaking down over time, typically in weight-bearing joints like the knees and hips. It tends to be asymmetrical, meaning it may affect one knee but not the other, and it’s most common in older adults.
RA works differently in almost every way. It most commonly strikes the small joints of the hands and feet, and it’s usually symmetrical, affecting the same joints on both sides of your body. It typically begins between ages 40 and 60, though it can start at any age. Women are two to three times more likely to develop it than men, a gap partly explained by sex differences in inflammatory markers like C-reactive protein, which runs higher in women even after accounting for body weight.
What Causes It
In RA, your immune system produces antibodies that form clusters called immune complexes. These complexes deposit in the synovium, the thin membrane that lines and lubricates your joints. Once lodged there, they trigger a chain reaction: complement proteins activate, blood vessel walls become more permeable, and immune cells flood into the joint lining. The synovium swells and thickens into an aggressive tissue called pannus, which gradually erodes cartilage and bone.
The inflammation is fueled by signaling molecules, particularly TNF-alpha and interleukin-1, which keep recruiting more immune cells and amplifying the damage. This understanding of the specific molecules involved has directly shaped modern RA treatments, many of which work by blocking these signals.
Recognizing the Symptoms
The hallmark symptoms of RA are painful, warm, swollen joints, most often in the fingers, wrists, and toes. The pattern is typically symmetrical. If your left hand’s knuckles are swollen, your right hand’s knuckles likely are too.
Morning stiffness is a key distinguishing feature. In RA, stiffness after rest lasts 45 minutes or longer, sometimes several hours. With osteoarthritis, stiffness usually eases within 15 to 30 minutes. RA also produces fatigue, low-grade fever, and loss of appetite, reflecting the fact that it’s a systemic disease rather than just a joint problem.
How It’s Diagnosed
No single test confirms RA. Doctors use a combination of physical examination, blood tests, and imaging to build a picture. Two blood markers are central to diagnosis. Rheumatoid factor (RF) is the older, more familiar test, but it’s positive in some people who don’t have RA, giving it a specificity of about 85%. Anti-CCP antibodies are more precise, with specificity around 95 to 96%, meaning a positive result is highly likely to indicate RA. Both tests have similar sensitivity (roughly 53 to 71% for anti-CCP), so a negative result doesn’t rule RA out.
Doctors also check inflammatory markers in your blood. Elevated levels indicate active inflammation somewhere in the body, which adds supporting evidence when joint symptoms are present. Under the formal classification system used internationally, doctors score four domains: how many and which joints are involved, blood test results, inflammation levels, and whether symptoms have lasted at least six weeks. A score of 6 out of 10 or higher points to RA.
Standard X-rays have long been the go-to imaging tool, but they often look normal in early RA because they can’t visualize the soft tissue inside the joint. Ultrasound detects bone erosions and joint inflammation earlier than X-rays and performs comparably to MRI. MRI has an edge in measuring the extent of inflammation in the synovium and bone marrow, making it useful when the diagnosis is uncertain or when doctors need a detailed baseline.
How RA Affects More Than Your Joints
Because RA is a systemic autoimmune disease, the inflammation doesn’t stay confined to your joints. Your cardiovascular system takes a significant hit. Women with RA face twice the risk of heart attack compared to women without it, and after 10 years of disease, that risk triples. The chronic inflammation stiffens artery walls and accelerates plaque buildup, even in people without traditional heart disease risk factors.
Lung involvement is more common than many people realize. Autopsy studies have found evidence of inflammation in the lining around the lungs in about 50% of RA patients, though only about 10% ever develop noticeable symptoms. Some people develop interstitial lung disease, where scarring in the lung tissue gradually reduces breathing capacity. This tends to occur in people who have had RA for many years and test positive for rheumatoid factor.
Eye problems affect a smaller but meaningful number of people. At least 10% of RA patients develop dry eyes (keratoconjunctivitis sicca), often as part of a secondary condition called Sjögren’s syndrome. More serious but rarer complications include scleritis, a painful inflammation of the white of the eye, and peripheral corneal ulceration, which can threaten vision if untreated.
Treatment Approach
The goal of RA treatment is remission, or at least the lowest possible level of disease activity. Treatment starts early and aggressively because joint damage in the first two years is often the most consequential. The cornerstone medications are called disease-modifying antirheumatic drugs, or DMARDs, which slow the immune system’s attack on your joints rather than just masking pain.
Traditional DMARDs, especially methotrexate, are the first line of treatment for most people. These medications broadly calm immune activity and can be remarkably effective. If they don’t bring the disease under adequate control, doctors add or switch to biologic DMARDs. Biologics are more targeted: some block TNF-alpha, the inflammatory molecule most responsible for joint destruction, while others target specific immune cells (B-cells or T-cells) or other signaling molecules called interleukins. A newer category called JAK inhibitors works on a different part of the immune signaling pathway and is taken as a pill rather than an injection.
The practical reality of treatment varies widely. A large population-level study in England and Wales found that about 35% of RA patients achieved remission within three months of starting treatment, and roughly 50% reached remission by 12 months. These rates held steady from 2018 through 2024, though there was notable geographic variation, ranging from 28% to 40% depending on the region. Under the strictest definition of remission, where every measure of disease activity must be near zero simultaneously, only about 13% of patients hit that mark at three months.
These numbers reflect how unpredictable RA can be. Some people respond quickly to the first medication they try. Others cycle through several treatments before finding the right combination. The treat-to-target approach, where your doctor adjusts medications every few months until reaching a specific goal, gives you the best odds of controlling the disease before irreversible joint damage sets in.