What Causes Septic Arthritis?The cause of this condition is a bacterial infection within a joint or joints (90 percent of such infections affect only one joint). These bacteria cause inflammation within the joint that can ultimately lead to damage to the cartilage (the slippery coating at the end of bones), underlying bone, and joint capsule.
There are several different types of bacteria that are known to cause septic arthritis. Among infants under one year of age, the most common cause of septic arthritis is Staphylococcus aureus or Group B Strep. In cases involving adults, the most common cause of septic arthritis is an infection with Neisseria gonorrhoeae (the bacteria that cause gonorrhea).
(Click Septic Arthritis Causes for more information on the causes of septic arthritis.)
Risk FactorsA risk factor is anything that increases a person's chances of developing a disease. Having risk factors for septic arthritis does not guarantee that a person will develop the condition; it just increases his or her chances of developing it.
Some risk factors for septic arthritis include:
- Age (infants and young children are at greatest risk for septic arthritis)
- Infection in another part of the body, especially infection within bone (known as osteomyelitis)
- Alcoholism or IV drug abuse
- Immunosuppressive medicines
- Rheumatoid arthritis, gout, or osteoarthritis
- Previous joint damage
- A history of recent steroid injections into the joint
- Having recently undergone certain surgical procedures (such as a knee replacement, hip replacement, or knee arthroscopy).