Within the context of rehabilitation protocols, biomechanical torque is an important metric majorly assessed indirectly with common mechanical exercising equipments. This paper presents a novel approach to torque-aimed rehabilitation applications using a portable knee orthosis designed as an isometric dynamometer for different joint-angle exercises. The orthosis presents a compact, lightweight and robust design, allowing for easy use in various settings. It also features a combination between an commercial orthotic structure and customized 3D-printed parts within a modular design. A simple and cost-efficient electronic system is designed based in joint action upon a single linear Load-Cell, associated with a peripheral embedded system. Once with the orthotic system built and assembled, there were performed bench tests for structural resistance assessment, which showed satisfactory results up to the range defined in the project’s scope of 38Nm. Additionally, this paper also presents a calibration protocol for weight correction, which serves for system modeling validation upon the load cell’s original output signal. The final regression model correctly replicates an linear system and presents an average error of 2.7% in comparison with the reference calibration weight. Overall, the proposed knee orthosis dynamometer represents an initial solution in biomechanical torque measurement in rehabilitation protocols, offering a portable, versatile and cost-efficient solution for assessing and improving knee joint function. Future works will focus in experimental performance of the orthotic system with individuals in rehabilitation routines and comparison with gold-standard dynamometers.