Abstract: A prosthetic ankle which can be easily and inexpensively manufactured and installed in conventional rigid prosthetic legs comprises opposing oblong plates having peripheries which are shaped to match the ankle portion of the leg in which the prosthetic ankle will be installed. Hinge structure bisects the inner surfaces of the plates and rotatably connects the plates, one of which is secured to a lower leg surface and the other to an upper foot surface. The plates may be sloped fore and aft to allow vertical rotation of the foot relative to the leg about the hinge axis. Biasing structure acts to return the foot to a position perpendicular to the leg and provide increased biasing with increased bending. The ankle allows small lateral rotations of the foot. The invention also provides for an auxiliary attachment, such that if an element of the ankle should fail the foot will remain secured to the leg.