Any sort of malpositioning of anterior cruciate ligament (ACL) replacement leads to an overload of single fibers of the ACL replacement. As long as this does not result in a tear of these fibers so that isometry of the ACL replacement is restored, the abnormal forces acting in and on the ACL replacement are transmitted from the ACL replacement to the remainder of the knee joint structures. We assumed that the posterior cruciate ligament (PCL) is notably affected. The present biomechanical model illustrates the relevant force vectors and reveals the extent of the effect of malpositioned ACL replacement on knee joint structures, particularly the PCL. Further investigations are needed to find out if the presumably occurring overload of a malpositioned ACL replacement can be calculated from its position on an individual basis. This may help deduce recommendations for ACL replacement procedures in the future.