Septic arthritis is potentially a life-threatening disease and frequently afflicts the most fragile patients. It is crucial to rule-out this diagnosis in a patient presenting with monoarticular arthritis, and the gold-standard is aspiration of the joint. A primary site of infection such as endocarditis or spondylodiscitis must be excluded by appropriate examination and investigative studies. The usual infecting organisms causing septic arthritis are Staphylococcus and Streptococcus species, and in young adults Gonococcus must be considered. Antibiotics should be started promptly after obtaining joint fluid for bacteriologic studies. Efficient drainage and lavage of the joint should be performed without delay because articular cartilage can be damaged quickly. Arthroscopy is a well-accepted technique in treating septic arthritis, particularly when the knee is involved.