JAMA PATIENT PAGE The Journal of the American Medical Association

BONE AND JOINT DISEASE

Septic Arthritis

S
eptic arthritis is an infection in a joint. The infection can be caused by bacteria, viruses, or, less frequently, by fungi
or parasites. Usually the infection involves a single large joint, such as the knee, but many joints may be involved.
The initial infectious process can begin elsewhere in the body and travel through the bloodstream to the joint. Other
sources include open wounds, surgery, and unsterile injections. Young children and elderly individuals are most likely to
develop joint infections. The April 4, 2007, issue of JAMA includes an article that categorizes clinical findings that help
identify patients who may have septic arthritis.

SIGNS AND SYMPTOMS FOR MORE INFORMATION

• Fever • Swelling (increased fluid within the joint) • American Academy of Orthopedic
• Chills • Warmth (the joint is red and warm to Surgeons (AAOS)
• Severe pain in the affected joint, touch due to increased blood flow) www.aaos.com
especially with movement • Fatigue and generalized weakness • Arthritis Foundation
RISK FACTORS www.arthritis.org

• Weak immune system—people with diabetes, kidney and liver problems, and HIV INFORM YOURSELF
infection, and those taking drugs that suppress their immune system have an impaired To find this and previous JAMA Patient
ability to fight against infections. Pages, go to the Patient Page link on
• Alcohol or other drug abuse JAMA’s Web site at www.jama.com.
• Cancer Many are available in English and
• Previous joint problems—conditions that affect joints, including other types of arthritis, Spanish.
may increase risk of septic arthritis. Previous joint surgery, joint replacements, and joint Sources: Arthritis Foundation, American Academy
injuries also increase risk. of Family Physicians, American Academy of
Orthopedic Surgeons
• Skin wounds—open skin wounds give bacteria easy access to the body.
Arthrocentesis of the Knee
SCREENING AND DIAGNOSIS
• Blood tests—to identify an increase in white blood cells (WBCs) and bacteria FEM
UR
• X-ray—to identify swelling within a joint and throughout the surrounding Patella (Kneecap)
soft tissues
• Arthrocentesis—a needle can be inserted into the joint and a sample of
Synovial Membrane
synovial (joint) fluid obtained for evaluation. Synovial fluid normally (Around Joint Space)
appears clear. Bacterial infections can alter the color, consistency, volume, TI
B
and makeup of normal joint fluid. Analysis of the sample can determine IA

the number of WBCs along with the type of bacteria. Synovial Fluid

• Diagnostic tests—a variety of tests can be used to identify the presence

and extent of an infectious process. Nuclear scans (using dyes and x-ray),
magnetic resonance imaging, and computed tomography are commonly used.
CROSS SECTION THROUGH KNEE
TREATMENT
Patella
Definitive diagnosis of an infectious process relies on the identification of the Synovial
pathogen (disease-causing organism) in stained smears from synovial fluid Membrane

and isolation of the pathogen from cultures of synovial fluid. Prompt treatment FEM
Joint Space
UR and Fluid
includes antibiotics (usually for 4 to 6 weeks taken orally or by vein). Often, the
infected joint space must be drained to eradicate the infection, hasten recovery,
and reduce pain. This can be done by repeated arthrocentesis, by surgical TIB
IA
irrigation (washing the joint out with sterile solutions), or by debridement
(removal of decaying tissue). Septic arthritis can lead to joint damage and
destruction, eventually requiring joint replacement surgery.
John L. Zeller, MD, PhD, Writer The JAMA Patient Page is a public service of JAMA. The information and recommendations
appearing on this page are appropriate in most instances, but they are not a substitute for
medical diagnosis. For specific information concerning your personal medical condition, JAMA
Cassio Lynm, MA, Illustrator suggests that you consult your physician. This page may be photocopied noncommercially
by physicians and other health care professionals to share with patients. To purchase bulk
Richard M. Glass, MD, Editor reprints, call 203/259-8724.

1510 JAMA, April 4, 2007—Vol 297, No. 13

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