The current document is directed to a two-way, by-passable, overrunning clutch incorporated within a mechanical prosthetic knee that provides functionality similar to a biological knee or incorporated in another articulated device, such as a robotic or orthotic articulated device or member. The currently disclosed two-way, by-passable, overrunning clutch allows for two-way free rotation when disabled, but, when enabled, prevents rotation in one direction while allowing free rotation in the other direction. In the mechanical prosthetic knee, the two-way, by-passable, overrunning clutch is enabled by application of a mechanical force and disabled by removal of the mechanical force.