Abstract: An artificial polycentric knee-joint mechanism comprising a four-bar linkage arranged to provide a motion similar to a normal knee having positive stability during ambulation. The four bars include a knee-mounting block mounted to the stump-receiving socket member and a lower linkage support-carriage member affixed to the lower limb component, the mounting block and linkage support being operably interconnected by side bar links, one of which is tension controlled. Also, included is a braking control to insure normal swing phase movement of the artificial leg and a shock absorbing device to prevent excess terminal impact when the lower limb returns to the extended position of the leg prosthesis.