The following population groups are at risk of developing septic arthritis after anterior cruciate ligament reconstructions: professional athletes, those who are allergic to penicillin, and those with immunosuppressive diseases. Staphyllococus aureus is the most common cause of infection. The patients with the hamstring autografts have a higher risk than those with the patellar tendon grafts. Preventive measures that should be performed include aseptic conditions in operative rooms, irrigation of the graft before its placement into the bone tunnels, experience of surgeon and proper antibiotics.