A tissue resecting instrument includes an end effector assembly having a proximal hub housing, a retainer cap extending proximally therefrom, an elongated outer shaft extending distally from the proximal hub housing, an inner cutting shaft rotatably disposed within the elongated outer shaft, and an inner core drive assembly that includes a proximal driver and a distal driver. The distal driver is coupled to the inner cutting shaft such that rotation of the distal driver rotates the inner cutting shaft relative to the elongated outer shaft. The proximal driver is slidable relative to the distal drive between a more-proximal position wherein the proximal driver is engaged with the retainer cap to rotationally fix the proximal driver, thereby rotationally locking the inner cutting shaft, and a more-distal position wherein the proximal driver is disengaged from the retainer cap permitting rotation thereof thereby permitting rotation of the inner cutting shaft.
