The lower extremity exoskeleton comprises two leg supports connectable toperson's lower limbs and configured to rest on the ground during their stancephase. Each leg support comprises a thigh link and a shank link； a knee jointconfigured to allow flexion and extension between the shank link and the thighlink. The lower extremity exoskeleton further comprises an exoskeleton trunkconnectable to the person's upper body. The exoskeleton trunk is connectableto the thigh links of the leg supports allowing for the flexion and extensionbetween the leg supports and the exoskeleton trunk. Two torque generators arecoupled to each of the knee joints. A power unit, capable of providing power,is coupled to the torque generators. In operation when a leg support is in astance phase and climbing a slope or stairs, the power unit injects power intothe respective torque generator thereby extending the respective knee angle.When a leg support is in stance phase and not climbing a slope or stairs, thepower unit does not inject any power to the respective torque generator, butwithout dissipating any stored power in said power unit, it forces the torquegenerator to resist flexion of the respective knee joint. When a leg supportis in a swing phase, the power unit does not inject any power to therespective torque generator, but without dissipating any stored power in saidpower unit, it forces the torque generator to minimize its resistance to kneeflexion and extension.
