An ultrasonic surgical instrument, comprising: (a) a shaft assembly, comprising: (i) a proximal shaft portion extending along a first longitudinal axis, (ii) an articulation assembly, (iii) a distal shaft portion extending distally from the articulation assembly, and (iv) an ultrasonic waveguide, wherein the ultrasonic waveguide extends through the proximal shaft portion, at least a section of the articulation assembly, and the distal shaft portion; (b) an end effector extending distally from the distal shaft portion, wherein the articulation assembly is configured to deflect the end effector toward and away from the first longitudinal axis between a straight configuration and an articulated configuration, wherein the end effector comprises: (i) an ultrasonic blade extending from the ultrasonic waveguide, wherein the ultrasonic blade defines a second longitudinal axis, and (ii) a clamp arm configured to actuate relative to the ultrasonic blade between an open configuration and a closed configuration in order to grasp tissue; and characterised by (c) a clamp arm drive tube comprising a clamp arm coupling, wherein the clamp arm drive tube is configured to drive translation of the clamp arm coupling in order to actuate the clamp arm between the open configuration and the closed configuration while the end effector is in the articulated configuration, wherein the clamp arm drive tube is also configured to rotate the clamp arm coupling in order to drive rotation of the clamp arm relative to the ultrasonic blade about the second longitudinal axis while the end effector is in the articulated configuration. (a) a shaft assembly, comprising: (i) a proximal shaft portion extending along a first longitudinal axis, (ii) an articulation assembly, (iii) a distal shaft portion extending distally from the articulation assembly, and (iv) an ultrasonic waveguide, wherein the ultrasonic waveguide extends through the proximal shaft portion, at least a section of the articulation assembly, and the distal shaft portion; (i) a proximal shaft portion extending along a first longitudinal axis, (ii) an articulation assembly, (iii) a distal shaft portion extending distally from the articulation assembly, and (iv) an ultrasonic waveguide, wherein the ultrasonic waveguide extends through the proximal shaft portion, at least a section of the articulation assembly, and the distal shaft portion; (b) an end effector extending distally from the distal shaft portion, wherein the articulation assembly is configured to deflect the end effector toward and away from the first longitudinal axis between a straight configuration and an articulated configuration, wherein the end effector comprises: (i) an ultrasonic blade extending from the ultrasonic waveguide, wherein the ultrasonic blade defines a second longitudinal axis, and (ii) a clamp arm configured to actuate relative to the ultrasonic blade between an open configuration and a closed configuration in order to grasp tissue; and characterised by (i) an ultrasonic blade extending from the ultrasonic waveguide, wherein the ultrasonic blade defines a second longitudinal axis, and (ii) a clamp arm configured to actuate relative to the ultrasonic blade between an open configuration and a closed configuration in order to grasp tissue; and characterised by (c) a clamp arm drive tube comprising a clamp arm coupling, wherein the clamp arm drive tube is configured to drive translation of the clamp arm coupling in order to actuate the clamp arm between the open configuration and the closed configuration while the end effector is in the articulated configuration, wherein the clamp arm drive tube is also configured to rotate the clamp arm coupling in order to drive rotation of the clamp arm relative to the ultrasonic blade about the second longitudinal axis while the end effector is in the articulated configuration.