Preliminary kinematic evaluation of a new stance-control knee-ankle-foot orthosis

Abstract

Background: Stance-control knee-ankle-foot orthoses permit free knee motion in swing while providing knee flexion resistance in stance for individuals with quadriceps muscle weakness. However, some stance-control knee-ankle-foot orthoses require full knee extension to engage the knee-joint lock, thereby not providing knee support when climbing stairs or stepping over curbs. Stance-control knee-ankle-foot orthoses that do support a flexed knee are either heavy, bulky, expensive, offer a limited number of locking positions, or cause noise. This paper presents a preliminary kinematic evaluation of a new stance-control knee-ankle-foot orthosis that was designed to address these limitations.

Methods: Kinematic gait analysis was performed on three male knee-ankle-foot-orthosis users with knee extensor weakness in at least one limb (mean age: 56.3 years (SD 4.0)). Three walking trials were performed with the subjects' current knee-ankle-foot-orthosis and then the new stance-control knee-ankle-foot orthosis (non-randomized before-after trial). Subjects completed a questionnaire about the new stance-control knee-ankle-foot orthosis and current knee-ankle-foot-orthosis.

Findings: A mean increase in knee flexion of 21.1 degrees (SD 8.2) during swing and a greater total knee range of motion was found when walking with the new stance-control knee-ankle-foot orthosis. Two knee-ankle-foot-orthosis users experienced a reduction in pelvic obliquity and hip abduction angle abnormalities when walking with the stance-control knee-ankle-foot orthosis. Two out of three subjects preferred walking with the new stance-control knee-ankle-foot orthosis over their prescribed knee-ankle-foot-orthosis.

Interpretation: The new stance-control knee-ankle-foot orthosis permitted improved gait kinematics for knee-ankle-foot-orthosis users while providing knee support in stance and free knee motion in swing at appropriate instants in the gait cycle. Overall, the new stance-control knee-ankle-foot orthosis provided more natural gait kinematics for orthosis users compared to conventional knee-ankle-foot-orthoses.