An apparatus comprising: (a) a body; and (b) a shaft assembly in communication with the body, wherein the shaft assembly comprises: (i) an end effector positioned at a distal end of the shaft assembly, (ii) an articulation joint positioned at a proximal end of the end effector, (iii) a cam gear in communication with the end effector through the articulation joint, and (iv) a lock bar in selective communication with the cam gear, wherein the lock bar is movable between a distal position and a proximal position, wherein the lock bar is configured to impede the rotation of the cam gear when the lock bar is in the distal position, wherein the lock bar is configured to allow rotation of the cam gear when the lock bar is in the proximal position, (c) characterized in that: (i) the shaft assembly comprises first and second cam gears (230, 231), of which the said cam gear is the second cam gear, wherein the first cam gear is positioned at the distal end of the shaft assembly, wherein the first cam gear is configured to rotate, wherein the second cam gear is operable to drive articulation of the end effector at the articulation joint, and (ii) the lock bar is in selective communication with the first cam gear, wherein the first cam gear is configured to drive the lock bar from the distal position to the proximal position through rotation of the first cam gear. (a) a body; and (b) a shaft assembly in communication with the body, wherein the shaft assembly comprises: (i) an end effector positioned at a distal end of the shaft assembly, (ii) an articulation joint positioned at a proximal end of the end effector, (iii) a cam gear in communication with the end effector through the articulation joint, and (iv) a lock bar in selective communication with the cam gear, wherein the lock bar is movable between a distal position and a proximal position, wherein the lock bar is configured to impede the rotation of the cam gear when the lock bar is in the distal position, wherein the lock bar is configured to allow rotation of the cam gear when the lock bar is in the proximal position, (i) an end effector positioned at a distal end of the shaft assembly, (ii) an articulation joint positioned at a proximal end of the end effector, (iii) a cam gear in communication with the end effector through the articulation joint, and (iv) a lock bar in selective communication with the cam gear, wherein the lock bar is movable between a distal position and a proximal position, wherein the lock bar is configured to impede the rotation of the cam gear when the lock bar is in the distal position, wherein the lock bar is configured to allow rotation of the cam gear when the lock bar is in the proximal position, (c) characterized in that: (i) the shaft assembly comprises first and second cam gears (230, 231), of which the said cam gear is the second cam gear, wherein the first cam gear is positioned at the distal end of the shaft assembly, wherein the first cam gear is configured to rotate, wherein the second cam gear is operable to drive articulation of the end effector at the articulation joint, and (ii) the lock bar is in selective communication with the first cam gear, wherein the first cam gear is configured to drive the lock bar from the distal position to the proximal position through rotation of the first cam gear. (i) the shaft assembly comprises first and second cam gears (230, 231), of which the said cam gear is the second cam gear, wherein the first cam gear is positioned at the distal end of the shaft assembly, wherein the first cam gear is configured to rotate, wherein the second cam gear is operable to drive articulation of the end effector at the articulation joint, and (ii) the lock bar is in selective communication with the first cam gear, wherein the first cam gear is configured to drive the lock bar from the distal position to the proximal position through rotation of the first cam gear.