Human-beings lose their neural ability to walk either fully or partially due to stroke, and consequently, the stroke survivors struggle to maintain a natural gait cycle during walking. a knee orthotic device helps to regain their lost ability with the help of a robotic structure. the traditional knee orthotic devices used a direct drive mechanism comprised of motor and gear assembly. this arrangement was seen to increase the power consumption and weight of the knee orthotic device. besides, it could limit the knee angular velocity and introduce non-linearity into the system due to backlash and friction. additionally, direct-drive actuators are not intrinsically safe for human-machine interaction. compliance mechanisms like series elastic actuators and lever-based compliance actuators were introduced to tackle the issues of using the direct-drive mechanism mentioned above. in the compliance mechanism, the power requirement at an instant is reduced by storing the spring energy and releasing it, whenever it is required. however, the existing compliance mechanisms increased the design complexity by using more than one motor to reduce power consumption, which indirectly affects the cost, weight, and size of the orthotic device. this study proposes a novel design of a knee orthotic device, where we focused on the betterment of energy economy with the help of a novel compliance actuation mechanism, namely a four-bar controlled compliance actuator (fcca). in fcca, a four-bar mechanism is used to modify the stiffness of the series spring in the stance phase, and the same fcca is utilized to achieve knee flexion in the swing phase. fcca tries to reduce the peak torque requirement at the motor to provide adequate stiffness to assist the knee joint during the single support phase. alike the other compliance mechanisms, fcca utilizes the storing and releasing of the spring energy to reduce power requirement at an instant. apart from this, fcca introduces a special design of a rocker arm that could amplify the input motor power. in the swing phase, the same fcca is utilized to flex the knee joint with the help of a pulley arrangement. an optimization algorithm is used to achieve the desired characteristics of the proposed knee orthotic device. it has helped to achieve a proper selection of design parameters to maximize the amplification of input motor power. the results found from analytical study and optimization are validated through simulation and bench testing. for bench testing, a 3d printed prototype has been designed. the results from simulation and bench testing have shown good agreement with that obtained using analytical study and optimization. a torque amplification equal to 9.43 is achieved from the bench testing. the main advantage of using fcca over other existing mechanisms is to reduce the power requirement by amplification of input motor torque without affecting the knee angular velocity much. in fcca, the power requirement is reduced utilizing the spring elasticity and by amplification of the motor power. the proposed design uses one motor to achieve the same. thus, it helps to minimize the weight and cost of the orthotic device as well. the current version of the prototype weighs 1.08 kg including motor, gears, motor driver, sensors and other electronic components.