Septic Arthritis Causes
A bacterial infection within a joint or joints is what causes septic arthritis. Different types of bacteria can cause the condition. Researchers have identified certain risk factors for septic arthritis. Although these risk factors are not "causes" of the disease per se, they can increase a person's chances of developing septic arthritis.
What Causes Septic Arthritis?The cause of septic arthritis is a bacterial infection within a joint or joints. 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.
Causes of Septic Arthritis by Age
In infants under one year of age, the most common septic arthritis cause is Staphylococcus aureus or Group B Strep. Haemophilus influenzae and Staphylococcus aureus are the most common causes in children under five years of age. Staphylococcus aureus is the most common cause in children five years of age and older. For adults, the most common cause of septic arthritis is an infection with Neisseria gonorrhoeae (the bacteria that cause gonorrhea).
Mycobacterium tuberculosis, which causes tuberculosis (TB), can also cause septic arthritis. Infection with the bacteria that causes Lyme disease (Borrelia burgdorferi) may also lead to septic arthritis.
Septic Arthritis Risk FactorsArthritis research scientists have shown that people with certain risk factors are more likely than others to develop septic arthritis. A risk factor is anything that increases a person's chances of developing a disease. Having risk factors for septic arthritis, however, 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 the condition)
- Infection in another part of the body, especially infection within bone (known as osteomyelitis)
- Alcoholism or IV drug abuse
- Immunosuppressive medicines
- Chronic arthritis
- Rheumatoid arthritis, gout, or osteoarthritis
- Previous joint damage
- A history of recent steroid injections into the joint
- Having recently undergone certain procedures, such as knee replacement, hip replacement, or knee arthroscopy.