A multi-articulated link knee joint capable of detecting a bending angle of a knee section without causing problems of an installation space and wiring of a sensor is provided. A four-link knee joint (10) includes a knee section (30) of a four-link mechanism, a fluid cylinder (40) that restrains an action of the knee section (30), a position detecting device (60) that detects a position of a piston rod (42) with respect to a cylinder tube (41) as an extension and contraction amount of the cylinder (40), and a computer that acquires a bending angle of the knee section (30) by converting the position detected by the position detecting device (60).
