What is arthritis?

Arthritis, or "joint inflammation," is a general term for a group of more than 100 diseases. Arthritis is inflammation (swelling) in and around the body’s joints. (A joint is a point at which two or more bones come together, such as the hip or the knee.)

Inflammation is one of the body's natural responses to disease or injury. Inflammation can cause pain, stiffness, and swelling, as well as loss of movement in some patients. Some types of arthritis include osteoarthritis, rheumatoid arthritis, psoriatic arthritis and gout.

Arthritis limits everyday activities such as walking, dressing and bathing. In the United States, one in five adults (52.5 million) reports having arthritis that has been diagnosed by a doctor.

Arthritis is the leading cause of disability among Americans aged 15 and older. However, arthritis affects people in all age groups, including almost 300,000 children.

Other statistics about arthritis:

  • More than 27 million people in the United States have osteoarthritis.
  • An estimated 1.3 million have rheumatoid arthritis.
  • More than half of those with arthritis are under 65 years of age.
  • Nearly 60% of Americans with arthritis are women.

What causes arthritis?

The causes of most types of arthritis are not known. Scientists are studying how three major factors may play a role in certain types of arthritis:

  • Genetic (inherited) factors (“runs in the family”).
  • What happened during a person’s lifetime.
  • The person’s current lifestyle.

Although the exact causes of arthritis might not be known, there are several risk factors. A risk factor is a something that increases a person's chance of developing a disease or condition. Risk factors for arthritis include:

  • Age — The risk of developing arthritis, especially osteoarthritis, increases with age.
  • Gender — In general, arthritis occurs more often in women than in men.
  • Weight — Being overweight puts extra stress on the joints that support a person’s weight. This increases wear and tear, and the risk of arthritis.
  • Work factors — Jobs in which the worker has to keep doing the same movements over and over, or does a great deal of heavy lifting, can cause stress in the joints and/or an injury, which can lead to arthritis.

The pain of arthritis might be caused by different things, including inflammation of the synovial membrane (tissue that lines the joints), tendons, or ligaments; muscle strain and fatigue. A combination of these factors can have an effect on how strong the pain is.

The pain of arthritis can be very different for each person. Things that contribute to the pain include the amount of damage and swelling within the joint.

What are the symptoms of arthritis?

Different types of arthritis have different symptoms, which can be mild in some people and very strong in others. Osteoarthritis usually does not cause any symptoms outside the joint.

Symptoms of other types of arthritis might include fatigue (feeling tired), fever, a rash and the signs of joint inflammation, including:

  • Pain.
  • Swelling.
  • Stiffness.
  • Tenderness.
  • Redness.
  • Warmth.

Last reviewed by a Cleveland Clinic medical professional on 04/05/2016.


  • National Institute of Arthritis and Musculoskeletal and Skin Diseases: Arthritis and Rheumatic Diseases. Accessed 2/17/2020.
  • Centers for Disease Control and Prevention - Arthritis: Frequently Asked Questions (FAQs). Accessed 2/17/2020.
  • National Institute on Aging: Arthritis Advice. Accessed 2/17/2020.
  • Barbour KE, Helmick CG, Theis KA, et al. Prevalence of Doctor-Diagnosed Arthritis and Arthritis-Attributable Activity Limitation — United States, 2010–2012. Morb Mortal Wkly Rep. 2013;62(44):869-873. PubMed PMID: 24196662.

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