# Effects of Toe-Out and Toe-In Gaits on Lower-Extremity Kinematics, Dynamics, and Electromyography
###### Abstract  
Toe-in and toe-out gait modifications have received increasing attention as an effective, conservative treatment for individuals without severe osteoarthritis because of its potential for improving knee adduction moment (KAM) and knee flexion moment (KFM). Although toe-in and toe-out gaits have positive effects on tibiofemoral (TF) joint pain in the short term, negative impacts on other joints of the lower extremity may arise. The main purpose of this study was to quantitatively compare the effects of foot progression angle (FPA) gait modification with normal walking speeds in healthy individuals on lower-extremity joint, ground reaction force (GRF), muscle electromyography, joint moment, and TF contact force. Experimental measurements using the Vicon system and multi-body dynamics musculoskeletal modelling using OpenSim were conducted in this study. Gait analysis of 12 subjects (n = 12) was conducted with natural gait, toe-in gait, and toe-out gait. One-way repeated measures of ANOVA (\(p<0.05\)) with Tukey's test was used for statistical analysis. Results showed that the toe-in and toe-out gait modifications decreased the max angle of knee flexion by 8.8 and 12.18 degrees respectively (\(p<0.05\)) and the max angle of hip adduction by 1.28 and 0.99 degrees respectively (\(p<0.05\)) compared to the natural gait. Changes of TF contact forces caused by FPA gait modifications were not statistically significant; however, the effect on KAM and KFM were significant (\(p<0.05\)). KAM or combination of KAM and KFM can be used as surrogate measures for TF medial contact force. Toe-in and toe-out gait modifications could relieve knee joint pain probably due to redistribution of TF contact forces on medial and lateral condylar through changing lateral contact centers and shifting bilateral contact locations. Keywords: gait modification; toe-in and toe-out; electromyography; musculoskeletal model +
Footnote †: journal: Applied Soft  
(TF) contact force or knee joint reaction force (JRF), such as valgus knee bracing [4], variable-stiffness shoes [5], lateral wedges [6], and gait modification/retraining [7; 8]. Gait modification includes adjustments in trunk lean, walking speed, and the foot progression angle (FPA). It has been reported that gait modifications have a significant effect on ground reaction force (GRF) and knee adduction moment (KAM) during stance phases [9; 10; 11], the effects of which depend on participant type (age, gender, and with osteoarthritis or healthy), gait modification type, and implementation level of gait modification. Trunk lean is reported to be highly efficient in reducing peak KAM values, while potential adverse effects including lower back discomfort, imbalance, and difficulty in maintenance for a long time [12; 13]. Although the toe-in and toe-out gait patterns could alleviate the progression of knee OA (osteoarthritis), the detailed mechanism is still vague [14; 15]. Gait modification has showed positive benefits at the knee joint, but it might be associated with negative effects on other joints; the longer-term effects of the toe-in and toe-out gait modifications in patients with knee OA is unknown. Previous work reported that peak value of KAM is positively related to walking speed; however, whilst peak KAM reduces with decreasing walking speed, the load duration on the knee joint increases and the effect of gait modifications on neuromuscular function is less [16; 17]. [PERSON] et al. [18] reported that toe-in and toe-out with wider step width gaits seem to be viable options to reduce peak adduction moment but that sagittal and transverse knee loadings should be monitored. Controlling FPA implies modifying the gait by either toe-in or toe-out adjustment. Individualized toe-in and toe-out would lead to immediate quadriceps and hamstring co-contraction increases in healthy adults. However, after adjusting the gait for a short period of time, the co-activations of these muscles were not significant [11].