Abstract: A wearable passive exoskeleton device for sit-to-stand and/or stand-to-sit transfer includes a leg exoskeleton frame configured to be worn at a user's leg and a lever arm rotatably coupled to the leg exoskeleton frame so as to provide a handle for the user to move between a sitting position and a standing position (or between a kneeling position and a standing position). The lever arm is rotatable with respect to the leg exoskeleton frame between a stowed position and a deployed position. The lever arm may be a unidirectional lever arm configured to rotate only in a first rotational direction with respect to the leg exoskeleton frame such that a pushing or pulling force exerted in a second rotational direction transmits an assisting force to the user to assist in a sit-to-stand and/or stand-to-sit movement.