Septic Arthritis is also known as infectious arthritis, bacterial, or fungal arthritis. It is the purulent invasion of a joint by an infectious agent which produces arthritis. The condition is an inflammation of a joint that's caused by infection. Typically, septic arthritis affects one large joint in the body, such as the knee or hip. Less frequently, septic arthritis can affect multiple joints. Septic arthritis is considered a medical emergency. If untreated, it may destroy the joint in a period of days. The infection may also spread to other parts of the body.
Pathophysiology: The major consequence of bacterial invasion is damage to articular cartilage. This may be due to the particular organism's pathologic properties, such as the chondrocyte proteases of S aureus, as well as to the host's polymorphonuclear leukocytes response. The cells stimulate synthesis of cytokines and other inflammatory products, resulting in the hydrolysis of essential collagen and proteoglycans. Infection with N gonorrhoeae induces a relatively mild influx of white blood cells (WBCs) into the joint, explaining, in part, the minimal joint destruction observed with infection with this organism relative to destruction associated with S aureus infection.
Statistics: In many countries Haemophilus influenzae type b (Hib) is the second most common cause of septic arthritis in children. In Finland large-scale immunisation against Hib using conjugate vaccines began in 1986, four years after a multicentre prospective study of orthopaedic infections in children had started. Since 1982, including six years before and ten after starting routine Hib vaccination, there has been a major change in the pattern of septic arthritis. From 1982 to 1988, 32 of 61 cases (53%) were caused by staphylococci, 22 (36%) by Hib and 7 (11%) by other bacteria. Since 1988, Hib infection has disappeared, and one-third of cases of childhood septic arthritis has been eliminated. This change has allowed us to reduce initial antimicrobial therapy for such children to cover only Gram-positive cocci. The more limited treatment is safer, reduces cost, and simplifies treatment.