The prepatellar bursa and the olecranon bursa are the two bursae that are most likely to become infected, or septic.[10] Septic bursitis typically occurs when the trauma to the knee causes an abrasion, though it is also possible for the infection to be caused by bacteria traveling through the blood from a pre-existing infection site.[11] In approximately 80% of septic cases, the infection is caused by Staphylococcus aureus; other common infections are Streptococcus, Mycobacterium, and Brucella.[3]:p.