Abstract: A device to assist ambulation. The device includes an arcuate edge whose center of curvature is located substantially at a point of load transfer from the body to the frame of the device. That point moves in the ambulation direction as a consequence of rolling contact of the arcuate edge with the ground. The arc is not necessarily a circular arc. In one embodiment, the load transfer point is at the knee, and the device can increase the stride of a normal leg or can act as a prosthetic substitution for a missing lower part of a leg. In another embodiment, the load transfer point can be at the armpit, and the device becomes a support in the nature of a crutch that renders crippled ambulation surprisingly smooth and stable. In fact, the device is so stable that the user can at least partially be sling-supported by it. In another embodiment, the load transfer point is at the hand, and the device can be used as a cane.