The author presents an overview of the current diagnostic procedures and the scheme used at the author's Department. The article also deals with therapeutical trends including arthroscopic treatment of empyema. Antibiotics necessary for the treatment of the disease are administered empirically. Most often as antibiotics of "the first choice" are recommended penicilin antibiotics with the inhibitor of beta-lactamase. The author points out the necessity of an early and adequate treatment of the empyema of the knee joint as a prevention of serious sequelae on the affected joint. Key words: empyema of the knee joint, diagnosis, therapy.