The effective rocker shapes created by able-bodied (human) lower limb systems (roll-over shapes) have been useful for understanding lower limb function in walking. This paper describes the effects of walking speed, shoe heel height, added weight attached to the trunk, and shoe rocker radius on the characteristics of the physiologically produced roll-over shapes. In general, we have found that the able-bodied human responds to various conditions of level walking to maintain the same invariant roll-over shape. Able-bodied lower limb roll-over shapes measured during ramp walking are rotated in ways that could be mimicked using changes in equilibrium point (alignment) of prosthetic and orthotic components. New systems are becoming available and others are being developed to automatically adapt to different ramp surfaces. More research is needed to demonstrate the likely biomechanical benefits of these adaptable systems to their users.