Causes

Septic arthritis can be caused by bacterial, viral or fungal infections. Bacterial infection with Staphylococcus aureus (staph) is the most common cause. Staph commonly lives on even healthy skin.

Septic arthritis can develop when an infection, such as a skin infection or urinary tract infection, spreads through your bloodstream to a joint. Less commonly, a puncture wound, drug injection, or surgery in or near a joint — including joint replacement surgery — can give the germs entry into the joint space.

The lining of your joints has little ability to protect itself from infection. Your body's reaction to the infection — including inflammation that can increase pressure and reduce blood flow within the joint — contributes to the damage.