Articulating ultrasonic surgical instruments and systems

A surgical instrument includes a housing having an elongated body extending distally therefrom. The elongated body defines a first articulating portion and a second articulating portion. The elongated body defines a lumen therein. An end effector is supported at a distal end portion of the elongated body. A flexible waveguide extends through the lumen of the elongated body. A proximal end portion of the flexible waveguide connects to an ultrasonic transducer. A distal end portion of the flexible waveguide is connected with the end effector. the flexible waveguide defines a first articulating portion having a narrower thickness than a thickness of other portions of the flexible waveguide and a second articulating portion having a narrower thickness than a thickness of other portions of the flexible waveguide.