In the rehabilitation process, robotic structures can support the different medical-surgical actions. These recovery process activities often involve repetitive movements that must be performed several times at various amplitudes. Robotic structures for rehabilitation can be driven by three types of active drives, namely electric, pneumatic and hydraulic actuators. Pneumatic systems have become increasingly present in various market segments and are widely used in the industry, mainly due to their ease of maintenance, low cost, safety and applicability in various processes. Currently, the concept of Frugal Innovation is being discussed, which emerges as a way to produce effective and affordable products using fewer resources to reach less-served customers. Frugal Innovation is centered on saving resources, is characterized by simplicity and clarity and aims to reach the low-income market. This article proposes the application of Frugal development methods in the design of a lower limb rehabilitation system. With the application of frugal concepts, pneumatic actuators were chosen. The choice of the pneumatic cylinder is presented from the required pneumatic force. The application of the Frugal Innovation approach in the design of this type of products demonstrates the relevance of applying these methods in efforts to mitigate or reduce the growth of the technological gap between underdeveloped and developed countries.