Effects of different slopes on hip and ankle biomechanics of replaced and non-replaced limbs of patients with total knee arthroplasty during incline ramp walking

Abstract

Although knee biomechanics has been examined, hip and ankle biomechanics in incline ramp walking has not been explored for patients with total knee arthroplasty (TKA). The purpose of this study was to investigate the hip and ankle joint kinematic and kinetic biomechanics of different incline slopes for replaced limbs and non-replaced limbs in individuals with TKA compared to healthy controls. Twenty-five patients with TKR and ten healthy controls performed walking trials on four slope conditions of level (0°), 5°, 10° and 15° on a customized instrumented ramp system. A 3x4 (limb x slope) repeated analysis of variance was used to evaluate selected variables. The results showed a greater peak ankle dorsiflexion angle in the replaced limbs compared to healthy limbs. No significant interactions or limb main effect for other ankle and hip variables. The peak dorsiflexion angle, eversion angle and dorsiflexion moment were progressively higher in each comparison from level to 15°. The peak plantarflexion moment was also increased with each increase of slopes. Both the replaced and non-replaced limbs of patients with TKA had lower hip flexion moments than the healthy control limbs. Hip angle at contact and hip extension range of motion increased with each increase of slopes. Peak hip loading-response internal extension moment increased with each increase in slope and peak hip push-off internal flexion moment decreased with each increase of slope. Our results showed increased dorsiflexion in replaced limbs but no other compensations of hip and ankle joints of replaced limbs compared to non-replaced limbs and their healthy controls during incline walking, providing further support of using incline walking in rehabilitation for patients with TKA.