» Acute bacterial septic arthritis of the knee is an orthopaedic emergency and, if left untreated, can result in substantial joint degradation. » Important risk factors for development of septic arthritis include age of >60 years, recent bacteremia, diabetes, cancer, cirrhosis, renal disease, drug or alcohol abuse, a history of corticosteroid injection, a recent injury or surgical procedure, a prosthetic joint, and a history of rheumatoid arthritis. » The diagnosis is primarily based on history and clinical presentation of a red, warm, swollen, and painful joint with limited range of motion. Laboratory values and inflammatory markers from serum and joint fluid may serve as adjuncts when there is clinical suspicion of septic arthritis. » The initial and general antibiotic regimen should cover methicillin-resistant Staphylococcus aureus and gram-negative and gram-positive organisms. The antibiotic regimen should be specified following the culture results of the infected joint. » Operative management involves either arthrotomy or arthroscopy of the knee with thorough irrigation and debridement of all infected tissue. The Gächter classification is useful in establishing a prognosis or in determining the need for an extensive debridement.