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Septic Arthritis
(Infectious Arthritis)

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Medical Author:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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Medical Editor:

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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What is septic arthritis?

Septic, or infectious, arthritis is infection of one or more joints by microorganisms. Normally, the joint is lubricated with a small amount of fluid that is referred to as synovial fluid or joint fluid. The normal joint fluid is sterile and, if removed and cultured in the laboratory, no microbes will be found. With septic arthritis, microbes are identifiable in an affected joint fluid.

Most commonly, septic arthritis affects a single joint, but occasionally more joints are involved. The joints affected vary somewhat depending on the microbe causing the infection and the predisposing risk factors of the person affected. Septic arthritis is also called infectious arthritis.

What microbes cause septic arthritis?

Septic arthritis can be caused by bacteria, viruses, and fungi. The most common causes of septic arthritis are bacteria, including Staphylococcus aureus and Haemophilus influenzae. In certain "high-risk" individuals, other bacteria may cause septic arthritis, such as E. coli and Pseudomonas spp. in intravenous drug abusers and the elderly, Neisseria gonorrhoeae in sexually active young adults, and Salmonella spp. in young children or in people with sickle cell disease. Other bacteria that can cause septic arthritis include Mycobacterium tuberculosis and the spirochete bacterium that causes Lyme disease.

Viruses that can cause septic arthritis include hepatitis A, B, and C, parvovirus B19, herpes viruses, HIV (AIDS virus), HTLV-1, adenovirus, coxsackie viruses, mumps, and ebola. Fungi that can cause septic arthritis include histoplasma, coccidiomyces, and blastomyces.