Acute septic arthritis of the knee joint is an orthopedic emergency, potentially devastating, which can lead to high morbidity and may even be life-threatening. While any synovial joint can be infected, the knee is the most often affected joint and is involved in about 50 % of the cases. The infection is usually caused by a gram-positive bacteria. The diagnosis is made by synovial fluid aspiration, microbiological analysis and hematological investigations of inflammatory measures. Treatment requires emergency irrigation and debridement of the joint, and intravenous antibiotics. Surgical debridement can be performed either arthroscopically or via open arthrotomy. In recent years, arthroscopic treatment demonstrated more favorable outcomes with better functional outcomes, shorter operative time and hospital stays.