A prosthetic knee joint includes an upper part, a lower part which is arranged pivotably to the upper part, a fastening device arranged on the upper part for a proximal prosthetic element, a fastening device arranged on the lower part for a distal prosthetic element, a four-limbed joint system with four linkages articulatedly fastened to each other, which are each pivotable to each other around a pivot axis, wherein the upper part (10) is arranged on the joint system. The joint system may be mounted pivotably on the lower part from a starting position counter to a spring force during a stance phase flexion, and the action line of the spring force may be aligned such that a moment acting against an inflexion of the joint system is present.