In one embodiment, the exoskeleton structure is fastened to the body of the user by a brace and at the foot level. The exoskeleton includes at least one set of three joints corresponding to the hip abduction/adduction, the hip flexion/extension and the knee flexion/extension, wherein the architecture of the exoskeleton is compatible with a set of different removable, adaptable and backdrivable actuation units dedicated to each joints and remotely located around the trunk of the user to decrease inertia and mass on the distal segments, wherein each joint can be modularily let free, constrained by a visco-elastic mechanism or actuated by one corresponding actuation unit.