Design and Analysis of a knee-ankle-foot orthosis using torsional spring

Many people suffering from neuromuscular diseases, have some degree of limitations in their walking pattern. Knee-Ankle-Foot Orthoses (KAFOs) help correct patients’ gait pattern by supporting knee and ankle joints. Patients with quadriceps muscle weakness suffer from some restrictions in extension as well as in controlling their flexion during the gait cycle because of abnormal stiffness pattern of the knee joint. This paper addresses patients with quadriceps muscle weakness by designing an appropriate orthosis utilizing two different mechanisms for the stance and swing phases. Stance phase mechanism locks knee joint movement from the initial-contact up to the end of mid-swing phase and with regards to the orientation of the foot after mid-stance phase, the knee joint can flex freely. The required moment to reproduce the stiffness of a normal knee joint is calculated using the OpenSim software package in conjunction with the data collected from the motion analysis of each patient.
The required moment to modify the stiffness of the knee joint for two patients with different levels of muscle weakness was reproduced using a torsional spring. By designing patient-specific orthosis, the stiffness profile of normal joint for each patient with distinct level of muscle weakness can be reproduced, allowing patients to experience smother gait cycle. Using this orthosis not only improves the patient’s gait cycle but also prevents potential damage to healthy muscles.