An artificial joint for lower extremities, comprising an upper part, which has mechanisms for attaching to a user, and a lower part mounted thereon in a pivotal manner about a joint axis. The lower part can be bent in from an extended position into a flexed position. A force accumulator is associated with the joint and is loaded via a force transmission mechanism through a flexing movement of the upper part relative to the lower part and supports an extension movement of the lower part relative to the upper part at least over a part of the extension movement. The force transmission device exerts a maximum moment of extension at a bending angle between 45° to 80°.