Background and Objectives:Equinovarus deformity and knee hyperextension are the most common problems in stroke patients. Ankle foot orthosis (AFO) is commonly prescribed to improve these disorders in these patients, as well as gait parameters that are approved. The aim of this study is to investigate the effect of ankle alignment and rigid AFO footplate length on spatiotemporal parameters and knee joint angle in hemiplegic post-stroke patients. Materials and Methods:This quasi-experimental study was performed on 6 hemiplegic post-stroke patients using three rigid AFO modes, including neutral ankle angle with full-length foot-plate -conventionally aligned AFO (CAFO), neutral ankle angle with ¾ length foot plate (¾AFO), and 50dorsi-flexion ankle angle with full-length foot-plate (50DF AFO) to investigate the effect of the alignment and foot plate length on spatiotemporal parameters and knee joint angle. The 3D motion analysis system with a Vicon Camera was used to collect the spatiotemporal parameters data. Results:The mean walking speed of patients after using 50DF AFO was significantly higher compared to CAFO (P=0.036). The mean stride length, cadence and maximum knee extension angle in the stance phase during single limb support was not significantly different in the three different test modes of ¾AFO, CAFO, 50DF AFO (P > 0.05). Conclusion:The DF AFO with 50ankle angle increases the walking speed and also controls knee hypertension in the terminal stance phase, which can be due to the progression of tibia in the mid to late stance phase and the alteration of ground reaction force vector.