● Using a PD compensator and an adaptive PID for controlling the mechanical motor alongside a PD controller for FES control gave rise to adequate knee joint tracking control.
● The adopted decision-making approach for activating the FES controller could yield postponing the muscle fatigue as much as possible.
● The controller performance was not degraded owing to changing the knee reference trajectory.
Plain Language Summary 
Neural system injuries due to accidents or disorders often inflict untreatable disability on the afflicted patients. This could significantly affect patients’ quality of life. Rehabilitation techniques could be a practical approach for restoring daily activities for such patients. One well-known technology is applying exoskeleton systems wearable robots that can provide the required joint torques needed for human movement. In this manner, the exoskeletons are used to rehabilitate people who have a disability in a specific part of their body. Another well-known tool for rehabilitation is technologies that work based on Functional Electrical Stimulation (FES). The FES-based devices deliver the electrical pulses to the involved muscle nerves to restore movement. Considering the strengths and shortcomings of exoskeletons and functional electrical stimulation, it seems that combining these two technologies can cover up the defects related to each of them. Thus, in this research work, a new combination strategy has been proposed. The ability of the proposed approach for controlling the knee joint movement has been evaluated through simulation studies on the muscle-joint model. The results of the carried-out evaluations prove the promising performance of the proposed strategy.