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: Thirty-six children who had bacteriologically confirmed acute hematogenous osteomyelitis but did not have concurrent septic arthritis, and ten children who had confirmed acute hematogenous osteomyelitis and concurrent septic arthritis, were followed for one year to compare the changes in the C-reactive protein level in the blood, the erythrocyte sedimentation rate, and the white blood-cell count. In both groups, the mean C-reactive-protein values were high (eighty-four milligrams per liter in the children who had septic arthritis and osteomyelitis and sixty-five milligrams per liter in those who had osteomyelitis only) at the time of admission to the hospital. However, in the group that had septic arthritis, the increase was significantly higher (p < 0.01) as early as the second day and a normal level (less than twenty milligrams per liter) was reached significantly later (p < 0.001) than in the group that had osteomyelitis only (11 +/- 7 days compared with 6 +/- 3 days [mean and standard deviation]). The erythrocyte sedimentation rate showed the same tendency, but the difference in the rates between the groups did not become evident until the fifth to fourteenth days after admission. A normal erythrocyte sedimentation rate (less than twenty millimeters per hour) was reached in 25 +/- 12 days in the children who had septic arthritis and in 17 +/- 10 days in those who did not (p < 0.05).