Abstract: In various embodiments, a surgical instrument can comprise an end effector including a channel configured to support a staple cartridge and, in addition, an anvil pivotable between open and closed positions relative to the staple cartridge channel. The surgical instrument can further comprise a closure tube configured to at least partially surround the anvil and the staple cartridge channel to hold the anvil in a closed position. The closure tube can extend around the anvil a greater distance than the staple cartridge channel. The surgical instrument can further comprise a shaft and, in addition, an articulation joint pivotably connecting the end effector to the shaft. The articulation joint can further comprise a floating guide member which can guidably support a knife bar extending into the end effector and, at the same time, move independently of the end effector and the shaft to provide such support.