Infectious arthritis, as indicated by its name, is caused by an infection with bacteria, viruses, or fungi. Infections usually spread to the joints from the site of origin by way of the bloodstream, so it may be difficult to determine where the infection started. Once the infection reaches the joint, it can cause warmth, pain, and swelling, sometimes accompanied by fever and chills. Occasionally, infection is introduced directly, as with a puncture wound or major injury.

Infectious arthritis due to bacteria most often affects the knee, although infections that are caused by viruses are most likely to affect small joints like fingers or toes. People with other joint diseases, such as rheumatoid arthritis, are slightly more likely to develop infectious arthritis, although the overall frequency of infectious arthritis, even among people with existing joint problems, is relatively low.

Causes of Infectious Arthritis
Viruses are the most common cause of infectious arthritis, but bacterial infections tend to be the most serious.

Viral infections
Many viruses may trigger arthritis, including the viruses that cause colds and other respiratory infections, as well as more serious illnesses such as AIDS and hepatitis. Multiple joints can be affected at the same time, and the symptoms sometimes appear similar to those of rheumatoid arthritis. Treating the virus usually alleviates arthritic symptoms, although chronic conditions such as HIV infection and some forms of viral hepatitis can cause ongoing joint pain.

Bacterial infections
Lyme disease, which is caused by the bacterium Borrelia burgdorferi, is transmitted primarily through bites of deer ticks. An infected person may develop a large, round rash with a central, clear area known as a “bull’s-eye,” as well as fatigue and other flulike symptoms. But the symptoms may be subtle or mistaken for something else, so Lyme disease may not be diagnosed promptly. If Lyme disease goes untreated and advances, arthritis may develop. This type of arthritis usually affects one or both knees but can also affect other larger joints.

Arthritic joint pain also affects about a third of people with gonorrhea, a sexually transmitted bacterial infection. Staphylococcus bacteria, which can cause infections through cuts or breaks in the skin and through contaminated food, can be released in the bloodstream and spread to the knees and other joints, causing intense pain and swelling. If a staph infection is not treated promptly, it can cause serious joint damage within just a few days. Tuberculosis, a bacterial infection that usually affects the lungs, can cause arthritis in the spine and in other large joints, such as the knees or hips. Reactive arthritis and Reiter’s syndrome are caused by infection with bacteria in the genitourinary or digestive tracts.

Symptoms of Infectious Arthritis

  • joint inflammation, pain, and stiffness
  • symptoms typically in the knee, shoulder, ankle, finger, wrist, or hip joints
  • fever and chills
  • rashSource: everydayhealth.com