Biological Joint Loading and Exoskeleton Design

While assistive exoskeletons typically focus on the metric of metabolic cost, we hypothesize that exoskeletons of sufficient power density could also reduce knee joint loading, which is understood to be a risk factor for osteoarthritis. Using biomechanical locomotion data, we run a simple simulation of two types of exoskeletons: those that provide a parallel load-path to ground, and those that apply torque directly to the human knee joint. We find that the second type offers larger reductions at normal walking speeds and that the power density required for knee load reduction is much lower than for metabolic cost reduction.