Knee arthrodesis was a common procedure before development of prosthetic replacement surgery. At present the most important indication for this intervention is septic failure of knee prosthesis. Several techniques can be used and each procedure may offer advantages and disadvantages which have to be analyzed before surgery according to the patient. Intramedullary nailing and external fixation are the most common techniques used for knee arthrodesis and both procedures show favorable results in most patients. Persistent infection and incomplete bone fusion are the main complications of knee arthrodesis. Because of residual functional impairment, all the candidates to knee arthrodesis should be informed about the results expected after the operation and possible alternative methods of treatment.