This paper presents the development, modeling, and analysis of an autonomous active ankle prosthesis with two degrees of freedom (2-DoF), designed to reproduce movements in the sagittal (dorsiflexion/plantarflexion) and frontal (inversion/eversion) planes in order to enhance the stability and naturalness of the user’s gait. Unlike most commercial prostheses, which typically feature only one active degree of freedom, the proposed device combines a lightweight mechanical design, a screw drive with a stepper motor, and a microcontroller-based control system. The prototype was developed using CAD modeling in SolidWorks 2024, followed by dynamic modeling and finite element analysis (FEA). The simulation results confirmed the achievement of physiological angular ranges of ±20–22 deg. in both planes, with stable kinematic behavior and minimal vertical displacements. According to the FEA data, the maximum von Mises stress (1.49 × 10⁸ N/m²) and deformation values remained within elastic limits under typical loading conditions, though cyclic fatigue and impact energy absorption were not experimentally validated and are planned for future work. The safety factor was estimated at ~3.3, indicating structural robustness. While sensor feedback and motor dynamics were idealized in the simulation, future work will address real-time uncertainties such as sensor noise and ground contact variability. The developed design enables precise, energy-efficient, and adaptive motion control, with an estimated average power consumption in the range of 7–9 W and an operational runtime exceeding 3 h per charge using a standard 18,650 cell pack. These results highlight the system’s potential for real-world locomotion on uneven surfaces. This research contributes to the advancement of affordable and functionally autonomous prostheses for individuals with transtibial amputation.

This paper provides a comprehensive review of the structural features and biomechanical functions of modern passive and semi-active knee prostheses, followed by comparative analysis. Based on findings from scientific literature and engineering practice, a new conceptual knee prosthesis was developed using a modular design approach. The proposed structure was modeled in SolidWorks, and its kinematic behavior and structural integrity were quantitatively evaluated through finite element analysis (FEA). The knee module was specifically designed to integrate with previously developed ankle and foot prosthetic components via an adapter interface. This modular approach allows the prosthesis to be configured according to the individual clinical needs of the patient. Simulation results confirmed that the proposed design meets the requirements for motion accuracy and structural reliability. In future work, the physical prototype will be manufactured using 3D printing with PLA plastic as an initial test material, followed by fabrication with high-strength engineering plastics or metal alloys. This study represents a critical early step toward the development of a fully functional, adaptive lower-limb prosthetic system.