subject: Infectious Arthritis [print this page] Infectious arthritis, also known as suppurative or septic arthritis, is a very serious infection usually caused by bacteria, affecting the joint and its surrounding capsule and fluid (synovium). In children and young adults this infection usually originates from organisms in the bloodstream (the hematogenous route).
In some cases this type of infection arises from an infection of the tissues in proximity to the joint such as skin, underlying soft fatty tissue and muscles. In rare cases the cause of infectious arthritis is direct trauma to the joint, usually penetrating trauma.
Because of the proximity of the joint to the boney tissue under it, one of the most common complications of arthritis is osteomyelitis, meaning the infection penetrated the boney tissue. Therefore each patient with diagnosed septic/infectious arthritis is treated as if they have osteomyelitis (for the chances of dissemination of the bacteria are relatively very high).
The most common organisms to cause septic arthritis vary with age. In infants, ages younger than 2 months, the most common organisms infecting the joint are Group B Streptococcus, Staphylococcus Aureus, Neisseria Gonorrhoeae, E-Coli and Klebsiella Pneumoniae. Older children and adults have higher rates of infection with Strep. Pneumoniae, Haemophilus Influenza type b and other anaerobic bacteria, together with the previously mention organisms of infants.
The typical clinical onset of an infected joint is high fever (greater than 103 degrees F., or 38.0 C.), warm, red and swollen joint, often very tender when touched, causing severe pain during movement, and in some cases even inability to perform full joint movements (pseudoparalysis).
This onset is usually sudden, without any preceding symptoms or signs. As in other types of arthritis in children, the child may present with a new limp that will usually catch the eye of the parent and lead to seek medical diagnosis and care.
When septic arthritis is suspected, immediate diagnostic procedure must be taken such as blood tests and cultures, including sampling fluid from the joint itself for inflammatory cells and bacteria. Blood tests will usually show elevated white blood count (the most prominent sign of bacterial infection in the blood). It is important to start treatment based on clinical suspicion even when there aren't any results of blood and joint cultures, in order to not postpone treatment and increase the chance of severe complications. Septic arthritis is an indication for hospitalization with intravenous wide-range antibiotic treatment until more specific information about the exact organism is received.
