The introduction explains the general problems of knee joint replacement by artificial hinge-type prostheses, due to the reduction of the physiological "degrees of freedom" to only rotational movements around a horizontal axis. These problems are compared with the advantages of this type of prosthesis. Subsequently a description of some significant constructional characteristics of the hinge-type prosthesis, 13 given as there are placement of the joint, size of the contact surface, safety of the rotational device, design of the hinge-mechanism, the patella shield and the prosthetic stems as well as the breaking of dynamic forces, which all are subsequently compared in their values. Finally a hinge-type prosthesis is described with characteristics judged optimal according to our present scientific knowledge. We statistically evaluated our material of hinge-type prostheses with regard to final results and frequency of serious complications.