This review discusses control strategies for active lower extremity prosthetics and orthotics (P/O) in the context of daily locomotive activities. It highlights the challenges and opportunities in controlling these devices to interface with the user's sensory-motor system. A general framework for controlling portable gait-assistance devices is proposed, considering the interactions between the controller, user, environment, and device. The framework treats P/O devices as actors within an ecosystem, not as independent entities, to structure the next generation of intelligent and multifunctional controllers. The review discusses the role of each component of the framework in assisting locomotion, how their states can be sensed as inputs to the controller, and how various control strategies fit into a hierarchical scheme resembling the structure and function of the human central nervous system (CNS). Active and passive safety mechanisms are central to P/O design and control, and are critical for regulatory approval for real-world use. The review also considers modalities for artificial sensory substitution and feedback, which are important for seamless integration of the device's controller with the human user. It discusses the physiological and neurological basis of locomotion control, including the role of the CNS, spinal interneurons, and reflex mechanisms. It also addresses compensatory and assisted control of locomotion, the importance of understanding the user's capabilities and physiological constraints, and the use of various sensor modalities for motion intention estimation. The review covers different types of sensors, including supraspinal neural activity, peripheral neural activity, joint torques and positions, and alternative input modalities. It also discusses artificial sensory feedback and substitution, which are essential for the seamless integration of P/O devices with the user's sensory-motor system. The review emphasizes the importance of environmental interaction and the use of environmental context in control strategies. Finally, it outlines various control strategies, including shared control, finite-state machines, and electromyography, and their potential for improving the functionality and usability of P/O devices.This review discusses control strategies for active lower extremity prosthetics and orthotics (P/O) in the context of daily locomotive activities. It highlights the challenges and opportunities in controlling these devices to interface with the user's sensory-motor system. A general framework for controlling portable gait-assistance devices is proposed, considering the interactions between the controller, user, environment, and device. The framework treats P/O devices as actors within an ecosystem, not as independent entities, to structure the next generation of intelligent and multifunctional controllers. The review discusses the role of each component of the framework in assisting locomotion, how their states can be sensed as inputs to the controller, and how various control strategies fit into a hierarchical scheme resembling the structure and function of the human central nervous system (CNS). Active and passive safety mechanisms are central to P/O design and control, and are critical for regulatory approval for real-world use. The review also considers modalities for artificial sensory substitution and feedback, which are important for seamless integration of the device's controller with the human user. It discusses the physiological and neurological basis of locomotion control, including the role of the CNS, spinal interneurons, and reflex mechanisms. It also addresses compensatory and assisted control of locomotion, the importance of understanding the user's capabilities and physiological constraints, and the use of various sensor modalities for motion intention estimation. The review covers different types of sensors, including supraspinal neural activity, peripheral neural activity, joint torques and positions, and alternative input modalities. It also discusses artificial sensory feedback and substitution, which are essential for the seamless integration of P/O devices with the user's sensory-motor system. The review emphasizes the importance of environmental interaction and the use of environmental context in control strategies. Finally, it outlines various control strategies, including shared control, finite-state machines, and electromyography, and their potential for improving the functionality and usability of P/O devices.