The development of a new stance controlled orthotic knee joint

Abstract

This work relates to the development and evaluation of a new type of stance controlled orthotic knee joint intended for use in knee-ankle foot orthoses (KAFOs) of individuals with excessive lower-limb quadriceps muscle weakness. The knee joint utilizes a unique strategy that allows it to remain safely locked by default, except just prior to toe-off. In this way, the knee provides stability during the stance-phase and normal knee flexion during the swing-phase. The new knee joint was prototyped and clinically tested on an individual with poliomyelitis. Instrumented gait analysis was performed and spatiotemporal and kinematic gait measures were acquired. Compared to a KAFO with permanently locked knee joints, the new knee provided more normal kinematics, increasing swing-phase knee flexion form 0 degrees (locked knee) to 44 degrees with the stance control activated.  Other kinematic parameters were primarily unchanged.  Spatiotemporal parameters indicated that the individual walked at a slightly reduced speed with the new knee, when compared to a permanently locked knee.  This was attributed, at least in part, to the limited acclimation period that had been provided. Future work includes long-term testing of the device.