Relation between Kinetic Load and Knee/Ankle Joint Angle during the Stance Phase of Walking with a Plastic Ankle Foot Orthosis

Abstract

Prescription of a plastic ankle foot orthosis (PAFO) is currently based on the experience and intuition of the doctor. A systematic approach is necessary to establish prescription standards. In this study, we analyzed the mechanical load acting on PAFOs during the stance phase of walking using our previously developed measurement system. In addition, these values were compared between 5 healthy volunteers and 7 patients with hemiplegia. Large differences were observed in the knee joint angle from 70% to 100% gait cycle, which increased steeply to about 40° in the healthy volunteers but increased gradually to about 20° in the hemiplegic patients. Also, the maximum angle of the knee joint in the healthy volunteers was 1.26 times greater than that in the patients, while the minimum angle of the knee joint was 0.84 times smaller. The amount of deformation of the PAFO was about 1.87 times greater at the knee joint and about 1.31 times greater at the ankle joint in the healthy volunteers than in the hemiplegic patients. These results revealed differences in the mechanical load between healthy volunteers and hemiplegic patients that affected the PAFO in terms of the ankle joint and knee joint during stance phase.