Septic Arthritis

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Also known as: Infectious Arthritis; Bacterial Arthritis

What is septic arthritis?

Septic arthritis, also called infectious arthritis, is usually caused by a bacterial infection but may sometimes be caused by a fungal or viral infection. The infection may spread to the affected joint from elsewhere in the body or may be introduced to the joint during an injury or surgery. Septic arthritis can affect anyone at any age, but children under age 4 and older adults are most susceptible.

The condition is typically acute, quickly causing severe joint pain, inflammation and swelling, redness, joint immobility, and in some cases fever and chills; however, symptoms may evolve more slowly and the infection may become chronic. Septic arthritis can affect any joint but is most frequently found in the knee, hip, shoulder, wrist, elbow, and finger joints. Usually only one joint will be affected, but in some cases there may be more than one. This condition needs to be diagnosed and treated quickly because it can destroy joints in a short period of time.

Septic arthritis can occur in people who have had a recent traumatic joint injury, had joint surgery or joint replacement, or had a blood infection (bacteremia or septicemia). Microorganisms can spread from an original site of infection, such as the inner ear or urinary tract, into the blood and then into the joint space. Additional risk factors for septic arthritis include having certain underlying illnesses like diabetes or anemia, a weakened immune system or taking medications that suppress the immune system, and/or another condition that affects the joints, such as goutosteoarthritis, or rheumatoid arthritis. Those with skin conditions such as psoriasis, eczema, or skin infections are also at increased risk. 

The acute form of septic arthritis is usually caused by bacteria, such as staphylococci or streptococci. The most common cause is Staphylococcus aureus.

Sometimes the microorganisms that cause Lyme disease, HIV, viral hepatitis, parvovirus B19mumps, or rubella can infect a joint. Chronic septic arthritis, which tends to be less painful and slower to develop, is less common and tends to be caused by microorganisms such as Mycobacterium tuberculosis, which causes tuberculosis (TB), and Candida albicans, a yeast infection.

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