Also known as septic arthritis, this form of arthritis is the result of a bacteria, virus, or even fungal growths getting into the (synovial) fluid around a single joint. Septic arthritis rarely occurs in more than one joint at a time.
Typical sources of septic arthritis are staphylococcus and streptococcus. The HIV and Herpes viruses have also been identified, as have adenoviruses (otherwise known as the common cold), parvoviruses, or slapped cheek disease, and mumps. Fungi can also cause septic arthritis, though fungal infections occur more slowly and are less severe.
Age groups most often affected by infectious arthritis are young children and the elderly. Those with immune diseases, weakened immune systems (from cancer, diabetes and the like), or previous damage to joints from sports or heavy work are also more likely to develop septic arthritis.
Typical of other forms of arthritis, infectious arthritis causes generalized weakness, or malaise, as well as swelling, pain and warmth in the affected joint. Unlike any other form of arthritis with the possible exception of gout the pain is intense. Doctors can diagnose septic arthritis via a sample of the fluid around the affected joint. If the white cell count is very high, septic arthritis is virtually confirmed.
Doctors may also want an identification of the kind of infectious agent, whether bacterial, viral, or fungal, and may even want to identify the specific agent (i.e., streptococcus). Imaging via X-rays can help determine if septic arthritis has damaged the joint. Blood tests can also be used to monitor the infection during treatment. The most important thing to avoid, with infectious arthritis, is the loss of cartilage in the joint.
Treatment of septic arthritis is a two-pronged attack: medical personnel will drain the infected fluid, via arthroscopy, and administer powerful antibiotics intravenously. The first regimen of antibiotics will likely be broad-spectrum. Once the bacteria are identified, antibiotics will be targeted. The object is to clear the infection before the joint is permanently destroyed.