Identification of passive elastic joint moments in the lower extremities

Musculotendon actuators produce active and passive moments at the joints th ey span. Due to the existence of bi-articular muscles, the passive elastic joint moments are influenced by the angular positions of adjacent joints. T o obtain quantitative information about this passive elastic coupling betwe en lower limb joints, we examined the passive elastic joint properties of t he hip, knee, and ankle joint of ten healthy subjects. Passive elastic join t moments were found to considerably depend on the adjacent joint angles. W e present a simple mathematical model that describes these properties on th e basis of a double-exponential expression. The model can be implemented in biomechanical models of the lower extremities, which are generally used fo r the simulation of multi-joint movements such as standing-up, walking, run ning, or jumping. (C) 1999 Elsevier Science Ltd. All rights reserved.