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: Septic arthritis can occur at any age. When considering children, it occurs at a higher rate in those under 3 years of age, with the hip, knee and ankle being the most common joints affected. From age 3 to adolescence, Septic arthritis is uncommon, at which point incidence will increase again. This is due partly to the incidence of STI based Septic arthritis (such as Gonococcal arthritis in females with cervical Gonorrhoea). Septic arthritis is often seen in the elderly, immunosuppressed and those with chronic inflammatory arthritides (such as rheumatoid arthritis), as these are predisposing conditions.