There is no single official list of “three types of arthritis.” More than 100 forms exist, but the three most common types people encounter are osteoarthritis, rheumatoid arthritis, and gout. Each one has a different cause, affects joints in different ways, and requires a different treatment approach. About 21.3% of U.S. adults have been diagnosed with some form of arthritis, and the vast majority fall into one of these three categories.
Osteoarthritis: Wear and Tear on Cartilage
Osteoarthritis is the most common form of arthritis and the one most people picture when they hear the word. It develops when the cartilage cushioning the ends of your bones gradually breaks down. Without that smooth surface, bones begin to rub against each other, causing pain, stiffness, and swelling. It generates nearly 10 million office visits to physicians each year in the U.S. alone.
The breakdown process is more complex than simple “wear and tear,” though that phrase gets used constantly. Inflammation plays a central role: inflammatory signaling molecules build up inside the joint, triggering enzymes that actively dissolve cartilage proteins. The bone underneath the cartilage also changes, becoming a source of those same inflammatory signals. So the process feeds itself once it gets going.
Osteoarthritis most often shows up in the knees, hips, hands (especially the finger joints closest to the nails), and spine. It tends to develop gradually after age 50, though younger people can get it after a joint injury. Morning stiffness is common but usually lasts less than an hour. The stiffness often returns after long periods of activity or at the end of the day, which distinguishes it from inflammatory types of arthritis.
Risk factors include age, excess body weight (which puts more load on weight-bearing joints), previous joint injuries, and repetitive occupational stress on specific joints. There is a genetic component, but lifestyle factors are significant contributors. X-rays typically show narrowed joint space and bone spurs, and no blood test confirms the diagnosis. It’s identified through imaging and physical examination.
Rheumatoid Arthritis: The Immune System Attacks the Joints
Rheumatoid arthritis is fundamentally different from osteoarthritis. It’s an autoimmune disease in which the immune system mistakenly attacks the synovium, the thin membrane lining the inside of your joints. That membrane becomes inflamed and thickened, and if the disease goes untreated, it destroys the cartilage and bone within the joint.
The process starts when immune cells, including certain white blood cells, infiltrate the joint lining. They release a cascade of inflammatory molecules that recruit even more immune cells, creating a self-sustaining cycle of inflammation. Over time, the inflamed tissue forms a destructive layer called pannus that invades and erodes cartilage and bone. Key inflammatory signals driving this process include molecules that promote swelling, pain, and tissue breakdown.
Rheumatoid arthritis typically appears between ages 30 and 60 and is two to three times more common in women. It tends to affect joints symmetrically, meaning if your left wrist is inflamed, your right wrist likely is too. The small joints of the hands and feet are common early targets, though it can affect larger joints as well. Morning stiffness lasts longer than one hour, and the joints often feel warm and swollen.
Genetics account for roughly 40 to 50% of the risk for the most common subtype (called seropositive RA). A family history of the disease, particularly in first-degree relatives, increases your odds significantly. Smoking is the strongest environmental risk factor, accounting for an estimated 20 to 30% of the environmental risk. Two blood tests help with diagnosis: rheumatoid factor (RF) and anti-CCP antibodies. The anti-CCP test is 97% specific for RA when positive. However, about 20% of people with rheumatoid arthritis test negative on both blood tests, so doctors sometimes diagnose it based on physical examination and imaging instead.
Gout: Crystal Buildup in the Joint
Gout is a form of inflammatory arthritis caused by the buildup of uric acid crystals inside a joint. Your body produces uric acid when it breaks down substances called purines, which are found naturally in your body and in certain foods like red meat, organ meats, and some seafood. When uric acid levels in the blood stay too high for too long, needle-shaped crystals can form and deposit in joint tissue, triggering intense inflammation.
A gout attack is hard to mistake for anything else. It usually strikes suddenly, often in the middle of the night, and frequently targets the big toe first. The joint becomes extremely swollen, red, hot, and so tender that even the weight of a bedsheet can be excruciating. Attacks can last days to weeks, and without management, they tend to become more frequent over time and can affect additional joints like the ankles, knees, wrists, and fingers.
Gout is far more common in men than women, though women’s risk increases after menopause. Risk factors include a diet high in purines, heavy alcohol consumption (especially beer), obesity, kidney disease, and certain medications that raise uric acid levels. Diagnosis is confirmed by identifying uric acid crystals in fluid drawn from an inflamed joint, or by measuring elevated uric acid levels in the blood.
How to Tell Them Apart
The three types differ in who they affect, which joints they target, and how symptoms behave over time. Osteoarthritis develops gradually, worsens with activity, and tends to affect joints you’ve used heavily throughout your life. Rheumatoid arthritis causes prolonged morning stiffness, affects joints symmetrically, and can come with fatigue and a general feeling of being unwell because the immune system is in overdrive. Gout arrives suddenly, hits one joint at a time (at least early on), and produces the most dramatic visible inflammation of the three.
The underlying cause also matters for treatment. Osteoarthritis management focuses on reducing joint stress through weight management, physical therapy, and pain relief. Rheumatoid arthritis requires medications that suppress or modulate the immune system to prevent joint destruction. Gout treatment centers on lowering uric acid levels and avoiding dietary triggers. Each type has a distinct path, which is why getting the right diagnosis early changes what happens next.
Other Types Worth Knowing About
While osteoarthritis, rheumatoid arthritis, and gout are the most common, a few other forms are widespread enough to mention. Psoriatic arthritis develops in some people with the skin condition psoriasis and causes joint pain, stiffness, and swelling alongside skin plaques. It can look similar to rheumatoid arthritis but tends to affect joints asymmetrically and often involves the joints at the tips of the fingers. Ankylosing spondylitis primarily targets the spine and the joints connecting the spine to the pelvis, causing back pain and stiffness that worsen with rest. Juvenile idiopathic arthritis is the most common chronic arthritis in children, causing persistent joint swelling, pain, and stiffness before age 16.