High-Output Hydraulic Robotic Joints: Architecture, Coupled Physics, Integration, and Task-Usable Performance

Hydraulic actuation can deliver substantial force or torque within a restricted robotic limb, yet installed joint capability emerges from more than actuator pressure. This critical engineering review connects mechanical output mechanism, hydraulic source placement, installation site, and runtime hydraulic capacity in a multidimensional architecture taxonomy. Representative hardware spans legged and wheel-legged robots, humanoids, wearable systems, and manipulators. Pressure–area, flow–speed, and virtual-work relations are interpreted together with containment stress, fluid and structural compliance, leakage, friction, and heat rejection to explain the usable output envelope. Integration is treated as a redistribution of fluid-path volume, moving mass, losses, thermal load, and service interfaces across shared sources, embedded passages, valve-integrated modules, and electro-hydrostatic actuators. Task-usable joint capability is defined through hardware, operating-condition, energy-conversion, and validation boundaries. A source-specific evidence matrix shows that pressure and output are commonly reported, whereas matched output, efficiency, installed-boundary clarity, and duty qualification remain substantially less complete. The review therefore links architecture-conditioned physics to evidence-aware benchmarking and proposes measurable research priorities for high-pressure tribology, thermal management, lightweight integration, reconfiguration, sensing, and robot-level validation.