Because the term ‘arthritis’ encompasses over 100 different medical conditions, it is difficult to pin point just one cause of arthritis. However, based on the number of people who are diagnosed with arthritis, the vast majority – over 85% – are diagnosed with either osteoarthritis or rheumatoid arthritis.
In any of the disorders that carry the name arthritis, there is joint inflammation in an area where two bones meet. This pain and inflammation can be caused by the wear and tear of the joint, such as osteoarthritis or injury, or from an immune system gone awry, such as rheumatoid arthritis. The causes depend upon the type.
To better understand the pain, inflammation and swelling let’s take a short look at how a joint works. Inside of the area of the body where two bones meet, creating a joint, there are ligaments that hold the bones together. There is also cartilage that covers the surface of both bones and keeps the bony surfaces from rubbing together. Surrounding the entire joint is a capsule, called the joint cavity, filled with synovial fluid which nourishes the cartilage and the joint. This fluid is produced by the membrane that lines the cavity. When something goes wrong to cause the symptoms of arthritis, it will affect the cartilage, synovial fluid, membrane and the bones. (1)
Arthritis that occurs immediately, and may or may not leave permanent damage, is infectious arthritis. This is an inflammation of the joint brought on by an infection in the joint space. If left untreated it can result in total joint destruction. The infection often is a result of infected blood that leaks into the joint or from an inadvertent stab into the joint. For instance, if an elderly woman has an infection in her blood and falls, causing bleeding into the wrist joint, she can develop infectious arthritis in that joint. A young child who is out running and playing can experience a puncture wound near the knee joint and subsequently develop infectious arthritis in that joint. (2)
References:
(1) Arthritis Care: How Joints Work
http://www.arthritiscare.org.uk/AboutArthritis/Howjointswork
(2) University of Washington Orthopedics and Sports Medicine
http://www.arthritiscare.org.uk/AboutArthritis/Howjointswork
(3) University of Maryland Medical Center: Rheumatoid Arthritis
http://www.umm.edu/patiented/articles/what_causes_rheumatoid_arthritis_000048_2.htm
(4) Annals of Rheumatic Disease: Cigarette Smoking and Rheumatoid Arthritis Severity
http://www.ncbi.nlm.nih.gov/pubmed/9306868
(5) Arthritis.com: What is Osteoarthritis
http://www.arthritis.com/osteoarthritis_symptoms.aspx
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