This paper presents the comprehensive mechatronic design and preliminary experimental validation of a lower limb exoskeleton robot specifically engineered for rehabilitation training of individuals with gait impairments resulting from conditions such as stroke, spinal cord injury, or neuromuscular disorders. The proposed system is a modular, adjustable, back-drivable robotic orthosis that provides assisted movement for the hip and knee joints in the sagittal plane. The core mechanical design prioritizes patient safety, ergonomic comfort, and alignment with natural human kinematics, utilizing lightweight aluminum alloys and composite materials. The actuation system integrates high-performance brushless DC motors with harmonic drive reducers and series elastic elements to deliver smooth, compliant torque output, thereby ensuring a natural human-robot interaction. A hierarchical control architecture is implemented, featuring high-level gait trajectory generation based on physiological gait data and adaptive impedance-based low-level torque control to accommodate varying levels of patient impairment and participation. Preliminary benchtop tests and single-subject feasibility trials were conducted to evaluate the system’s mechanical integrity, control performance, and basic usability. Results indicate that the exoskeleton can accurately track prescribed rehabilitation trajectories with minimal error, provides stable and adjustable assistance, and demonstrates satisfactory mechanical robustness. The discussion elaborates on the implications of the mechatronic integration choices, the adaptability of the control strategy for different therapeutic paradigms, and the critical pathway towards full clinical trials. This work establishes a foundational platform for a safe, effective, and patient-adaptive robotic rehabilitation device, contributing to the advancement of technology-assisted neurorehabilitation.