This article was last reviewed on
This article waslast modified on
September 20, 2017.
What is arthritis?

Arthritis is the inflammation of one or more joints. Classic symptoms of arthritis include joint pain, swelling, stiffness, and redness. However, there are over 100 types of arthritis with varying manifestations.

Arthritis may be due to gradual wear and tear on the joints or result from an autoimmune disorder. It may be triggered by injury (such as a fracture) or infection (viral, bacterial, or fungal). A person may have more than one type of arthritis.

Arthritis affects both sexes and all ethnicities. Most types are more common in adults, but arthritis can occur at any age and can affect joints in many different parts of the body. Some specific types of arthritis include:

  • Osteoarthritis (OA) – the most common form of arthritis, affecting about 27 million people in the United States; it is chronic and results from the breakdown of cartilage in the joints; associated with the aging process and "wear and tear"
  • Rheumatoid arthritis (RA) – an autoimmune disorder that affects about 1.3 million people in the U.S.; nearly 3 times more women than men are affected by RA
  • Juvenile rheumatoid arthritis (JRA) – also called juvenile idiopathic arthritis (JIA); the most common type of childhood arthritis; involves at least 6 weeks of persistent arthritis in a child younger than 16 years of age
  • Gout – associated with excess uric acid that deposits needle-like crystals into affected joints, especially in the big toe, causing sudden and severe pain; most commonly affects men over the age of 30
  • Psoriatic arthritis – associated with the skin condition psoriasis; characterized by joint pain, stiffness and swelling in any part of the body
  • Septic arthritis – caused by an infection in a joint; it can result in serious joint damage in a short period of time if not treated promptly
  • Ankylosing spondylitis – a chronic form of arthritis that mainly affects the spine
  • Reactive arthritis – a form of arthritis that affects typically the knees, ankles, and feet and is also associated with inflammation of the urethra and the eyes (conjunctivitis or uveitis); it is so called because it normally occurs as a reaction to an infection somewhere in the body.

Some organizations classify fibromyalgia, Sjogren syndrome, scleroderma, and lupus (SLE) as types of arthritis as well.

Laboratory tests can be useful in diagnosing these forms of arthritis and/or ruling out other conditions that may cause similar symptoms. For more detailed information on these, click on the linked condition name to go to that article.

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

Arthritis Foundation. Do I Have Arthritis? Available online at http://www.arthritistoday.org/about-arthritis/do-i-have-arthritis/do-you-have-arthritis.php through http://www.arthritistoday.org. Accessed Sept 2013.

MayoClinic.com. Arthritis. Available online at http://www.mayoclinic.com/health/arthritis/DS01122 through http://www.mayoclinic.com. Accessed Sept 2013.

MayoClinic.com. Psoriatic arthritis. Available online at http://www.mayoclinic.com/health/psoriatic-arthritis/DS00476 through http://www.mayoclinic.com. Accessed Sept 2013.

MayoClinic.com. Juvenile Rheumatoid Arthritis. Available online at http://www.mayoclinic.com/health/juvenile-rheumatoid-arthritis/DS00018 through http://www.mayoclinic.com. Accessed Sept 2013.

Centers for Disease Control and Prevention. Arthritis Types. Available online at http://www.cdc.gov/arthritis/basics/types.htm through http://www.cdc.gov. Accessed Sept 2013.

Centers for Disease Control and Prevention. Childhood Arthritis. Available online at http://www.cdc.gov/arthritis/basics/childhood.htm through http://www.cdc.gov. Accessed Sept 2013.

National Library of Medicine. PubMed Health: Arthritis. Available online at http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002223/ through http://www.ncbi.nlm.nih.gov. Accessed Sept 2013.

Arthritis Foundation. Juvenile Arthritis. Available online at http://www.arthritis.org/conditions-treatments/disease-center/juvenile--arthritis/ through http://www.arthritis.org. Accessed Sept 2013.

Arthritis Foundation. Rheumatoid Arthritis. Available online at http://www.arthritis.org/conditions-treatments/disease-center/rheumatoid-arthritis/ through http://www.arthritis.org. Accessed Sept 2013.

Arthritis Foundation. Osteoarthritis. Available online at http://www.arthritis.org/conditions-treatments/disease-center/osteoarthritis/ through http://www.arthritis.org. Accessed Sept 2013.

Sources Used in Previous Reviews

(2009 August 26, Updated). National Institute on Aging. Arthritis Advice [On-line information]. Available online at http://www.niapublications.org/agepages/arthritis.asp through http://www.niapublications.org.

Arthritis Foundation. Juvenile Rheumatoid Arthritis. Available online at http://www.arthritis.org/disease-center.php?disease_id=38&df=definition through http://www.arthritis.org. Accessed October 2010.

Arthritis Foundation. Gout: Who is at risk? Available online at http://www.arthritis.org/disease-center.php?disease_id=42&df=whos_at_risk through http://www.arthritis.org. Accessed May 2010.

(April 2009) National Institute on Arthritis, Musculoskeletal and Skin Diseases. Health Information: Rheumatoid Arthritis. Available online at http://www.niams.nih.gov/Health_Info/Rheumatic_Disease/default.asp#ra_2 through http://www.niams.nih.gov. Accessed October 2010.

(Revised May 2006) National Institute on Arthritis, Musculoskeletal and Skin Diseases. Health Information: Osteoarthritis. Available online at http://www.niams.nih.gov/Health_Info/Osteoarthritis/default.asp#2 through http://www.niams.nih.gov. Accessed October 2010.

MedlinePlus Medical Encyclopedia. Septic Arthritis. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000430.htm. Accessed October 2010.