Septic arthritis, also called infectious arthritis, is an infection in a joint cavity. The infection may spread from another part of the body or it can be introduced directly to the joint during an injury, injection or surgery. Most commonly, septic arthritis results from bacterial infections caused by staphylococci, streptococci or Neisseria gonorrhoeae, but it may also be caused by a fungal or viral infection.
The condition is typically acute, quickly causing severe pain in a single joint. Symptoms include inflammation and swelling, redness, joint immobility, and in some cases fever and chills. Occasionally, symptoms may evolve more slowly and 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). Prosthetic joint infections are becoming increasingly common. Additional risk factors for septic arthritis include having certain underlying illnesses like diabetes or anemia, a weakened immune system or the presence of an indwelling catheter. Conditions such as gout, osteoarthritis, or rheumatoid arthritis may also predispose someone to septic arthritis. Approximately 45% of the people reported to have developed septic arthritis are over the age of 65. Those with skin conditions such as psoriasis, eczema, or skin infections are also at increased risk. In younger, sexually active adults, the most common cause is Neisseria gonorrhoeae.
Sometimes the microorganisms that cause Lyme disease, HIV, viral hepatitis, parvovirus B19, mumps, 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.