An apparatus comprises a body a shaft assembly an end effector and an articulation joint. The end effector is operable to manipulate (e.g. staple) tissue. The articulation joint couples the end effector with the shaft assembly and permits the end effector to deflect away from the longitudinal axis of the shaft assembly. The articulation joint comprises a locking assembly which is operable to selectively lock the angular position of the end effector relative to the longitudinal axis. The locking assembly comprises a first locking member and a second locking member. The first locking member is unitarily secured to the end effector. The second locking member is movable along a first axis to selectively engage the first locking member to thereby selectively lock the angular position of the end effector relative to the longitudinal axis of the shaft assembly. The first axis is perpendicular to the longitudinal axis.
