What Is Arthritis?

Understanding arthritis can help you manage it better and feel healthier. Learn more about the types of arthritis and how they differ.

By Linda Rath | Updated June 9, 2022

Arthritis isn’t a single disease; the term refers to joint pain or joint disease, and there are more than 100 types of arthritis and related conditions. People of all ages, races and sexes live with arthritis, and it is the leading cause of disability in the U.S. It’s most common among women, and although it’s not a disease of aging, some types of arthritis occur in older people more than younger people.

Common arthritis symptoms include swelling, pain, stiffness and diminished range of motion in joints. Symptoms vary from mild to severe and may come and go. Some may stay about the same for years, but symptoms can also progress and get worse over time. Severe arthritis can result in chronic pain, difficulty performing daily activities and make walking and climbing stairs painful and grueling.

Arthritis can also cause permanent joint changes. These may be visible, such as knobby finger joints, but often the damage can be seen only on X-rays. Some types of arthritis affect the heart, eyes, lungs, kidneys and skin as well as the joints.

Types of Arthritis


Osteoarthritis (OA) is by far the most common type of arthritis. It can damage almost any joint but mainly occurs in the hands, spine, hips and knees. OA was once considered a wear-and-tear disease in which cartilage — the protective layer on the ends of bones — wore down after years of use. But with further research, the thinking about OA has changed. Doctors now know that OA is a disease of the whole joint, not just cartilage. Bones in affected joints become weaker, the connective tissue that holds the joint together deteriorates and inflammation damages the joint lining. Contrary to decades of belief, inflammation plays a key role in OA, just as it does in most other types of arthritis.

There’s also a growing consensus that inflammatory OA is one of several subtypes of osteoarthritis. Other subtypes include OA associated with:

  • Post-traumatic injuries, such as a torn ACL or fracture
  • Work-related damage from physically demanding jobs, such as farming and construction
  • Lifestyle factors, including excess weight, lack of exercise and poor diet  

Although the prevalence of OA tends to increase with age, it’s not an inevitable part of growing older. You can help prevent joint problems by staying active, maintaining a healthy weight and limiting foods that stoke inflammation like red meat, highly processed foods and sugar. Better bets? Berries, leafy greens, wild salmon, whole grains and olive oil.

If you already have mild to moderate joint pain and stiffness, regular physical activity, hot and cold therapies, judicious use of over-the-counter pain relievers and assistive devices may help manage your symptoms.

When joint symptoms are severe, causing limited mobility and affecting quality of life, you may want to discuss a surgical solution with your doctor.

Autoimmune Inflammatory Arthritis

A healthy immune system is protective. It generates inflammation to clear infections and heal injuries. But in inflammatory arthritis, the immune system is overactive, attacking healthy tissue, including joints in the spine, hands and feet. In some people, inflammation becomes systemic, damaging the eyes, skin, heart and other organs. Many, but not all types of inflammatory arthritis are considered autoimmune diseases because the immune system loses the ability to distinguish self from not-self and attacks the body it’s supposed to protect.

Rheumatoid arthritis (RA) is the most common form of autoimmune inflammatory arthritis. Psoriatic arthritis (PsA) axial spondyloarthritis (axSpA), gout and juvenile arthritis are less common and can be more challenging to diagnose.

It’s not known what causes inflammatory arthritis in every person, but the general consensus is that something in the environment — a virus, stress or smoking, for examples — can trigger it in people who are genetically predisposed. Recent research has also highlighted the complex and critical role of gut microbes in immune-related inflammatory diseases like RA and PsA.  

The trillions of mostly friendly bugs that live in your gut, skin and mouth, collectively called the microbiome, regulate immune cells throughout the body and shape how the immune system functions in various diseases. When these vast microbial communities get out of balance due to poor diet, antibiotic treatment, stress or some other factor, they may no longer regulate the immune response in a normal way. This is thought to be one of the key contributing factors to RA and other autoimmune-related inflammatory conditions.

With autoimmune and inflammatory types of arthritis, early diagnosis and treatment are critical. Slowing disease activity can help minimize or prevent permanent joint damage as well as reduce pain and improve function and quality of life. Remission (defined as little to no disease activity) is always the goal, but low disease activity may be a more realistic target for some people.  

This is usually best achieved with a combination of medications and a healthy lifestyle — regular exercise, restful sleep, healthy food choices and less stress. The medication depends on the type of arthritis, the severity of symptoms and how well someone responds to a particular drug. For some people, the first medicine tried may not be the best fit. And some arthritis drugs can have unpleasant side effects or lose their effectiveness over time. It may take a few tries to find the right medication.

Infectious Arthritis

A bacterial, viral or fungal infection triggers infectious arthritis. It usually starts when an infection from another part of the body travels to a joint, usually the knee. Symptoms like swelling, pain and fever can be sudden and intense, but treatment with antibiotics or antifungals usually clears the infection pretty quickly. Most viral infections last a week or two and go away on their own. Some people with infectious arthritis may need to have their joint fluid drained to remove infected synovial fluid, reduce pain and inflammation and prevent joint damage.   

Gout (Metabolic Arthritis)

Metabolic or gouty arthritis — commonly known as gout — results from a buildup in joints of painful uric acid crystals. These are a byproduct of the breakdown of purines — substances normally found in human cells and many foods, especially red meat, organ meats, some seafoods and alcohol. Normally the body gets rid of excess uric acid, but when it doesn’t, it can accumulate in joints, causing sudden and intense bouts of pain, especially the big toe.

However, most people with high uric acid levels never develop gout and many gout patients have normal uric acid. Some research suggests that certain factors in addition to uric acid might trigger gout. Possible culprits include damage from OA, disruptions in the microbiome and even white blood cells in the fluid inside joints.

Some people experience only one gout attack, or flare, and never have other symptoms. They don’t typically require medication. People who have more than one gout flare or severe symptoms are typically prescribed uric acid-lowering drugs. Those drugs can have serious side effects (and may not address the real problem), so in addition to taking medication, patients are advised to adopt a mostly plant-based, low-purine diet, rich in fruit, vegetables, whole grains, olive oil and low-purine fish.

What You Can Do

The first step is to get an accurate diagnosis of what’s causing your joint pain. Talk to your primary care doctor about your symptoms. You may be referred to a rheumatologist or orthopedist, doctors who specialize in arthritis and other musculoskeletal conditions. Many things can be done to preserve joint function, mobility and quality of life. Learning about the disease and treatment options, making time for physical activity and maintaining a healthy weight are essential.

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