Post-operative septic arthritis is a rare but potentially devastating complication of primary anterior cruciate ligament reconstruction (ACLR). Patients with post-operative septic arthritis usually present within two weeks of an ACLR, with an increasingly painful knee joint, restricted range of motion, increasing effusion, local erythema and fever over 38.5 °C. Methods to prevent infection include cessation of smoking, treating Staphylococcus aureus colonisation, appropriate perioperative measures and meticulous surgical technique. The ‘vancomycin wrap’ technique is performed intraoperatively in addition to intravenous antibiotics. It is effective in preventing post-operative septic arthritis. The recommended management of post-operative septic arthritis involves arthroscopic debridement for source control combined with four to six weeks of intravenous antibiotic therapy and two to four weeks of oral antibiotics. The graft can be retained in 80% of cases with early intervention. With early intervention, patients can effectively be treated with no evidence of infection reoccurrence, maintain knee stability and achieve near complete range of motion.