Biomechanical changes such as increased knee adduction moment (KAM) during walking are known to be involved in the development and severity of knee osteoarthritis (OA). Although various foot progression angle (FPA) modifications during gait have been applied to reduce peak KAM, few studies have investigated effects of applying toe-in or toe-out walking modifications for knee OA on peak KAM and three-dimensional (3D) moments of the ankle joint. Kinetic moment variables were acquired from 35 individuals with medial knee compartment OA. A 3D motion analysis system and two force platforms were used to acquire KAM and 3D moments of both ankle joints during gait. Visual3D motion analysis program was used to obtain final moment data for statistical processing. Repeated-measures analysis of variance with Bonferroni adjustment was used to compare kinetic and kinematic values for each FPA walking condition. The first peak KAM of an internal rotation foot position of the FPA walking condition showed significant decrease compared to normal foot position walking (p < 0.01). The second peak KAM of an external rotation foot position walking showed significant decrease compared to normal foot position walking (p < 0.01). Compared to a normal foot position, peak ankle inversion moment of the external rotation foot position walking showed a significantly decrease (p < 0.05). There were no interactive effects between FPA condition and limb sides for any KAM values (p > 0.05). These results suggest that clinical application of toe-in or toe-out gait modification walking in individuals with knee OA should be performed based on biomechanical evaluations such as peak KAM.

Although Cable driven rehabilitation devices (CDRD) have advantages over traditional link-driven devices, including lightweight, ease of reconfiguration, remote actuation, etc, the majority of existing lower-limb CDRD is limited to rehabilitation in the sagittal plane. In this work, we extend our previous sagittal plane model (2DOF) to accommodate hip motion in the frontal plane (abduction/adduction) toward studying the feasibility of tracking bi-planar motion (combined frontal and sagittal plane motion) via intra-planar cable routing. Two optimization problems have been formulated to estimate an optimal location of the hip cuffs, first to estimate the optimal cuff location at each time step to identify a single ‘averaged’ optimal cuff location and second to calculate a single optimal cuff location for the entire gait cycle. The optimization solutions identified for the 3DOF model revealed that optimization of the location of cuffs on the anterior and posterior side of the hip joint for 4 cable configuration is not sufficient to generate the desired bi-planar motion. For simultaneous tracking of the bi-planar motion, 2 additional cables have been added at hip joints and are routed in an intra-planar manner. The simulation result with the 3DOF model confirmed successful bi-planar trajectory tracking. The various number of cables and cable routings for tracking bi-planar motion will be studied in future work.