A surgical apparatus includes a body, an ultrasonic transducer, a shaft, an acoustic waveguide, an articulation section, an end effector, and a restricting member. The ultrasonic transducer is operable to convert electrical power into ultrasonic vibrations. The shaft couples the end effector and the body together. The acoustic waveguide is coupled with the transducer. The articulation section is operable to flex to thereby deflect the end effector from a longitudinal axis defined by the shaft. The restricting member is operable to restrict lateral deflection of the end effector. The restricting member is further operable to cooperate with a translating member to rigidize the articulation section when the end effector is aligned with the longitudinal axis. Such rigidization includes removing any “play” or other small movement that might otherwise be provided by the articulation section due to manufacturing tolerances and/or looseness between parts.
