Proximal locking mechanism for colpotomy device

A knob locking assembly for a laparoscopic medical device is provided. The knob locking assembly includes a lock configured to engage the knob locking assembly with a drive tube housing of the laparoscopic medical device in extended and retracted positions where the knob locking assembly rotates but does not translate with respect to the drive tube housing when engaged. The knob locking assembly also has a biasing member that provides a biasing force for biasing the lock in each of the extended and retracted positions to lock out longitudinal translation of the rotatable drive assembly when the knob locking assembly is engaged with the drive tube. In addition, the knob locking assembly includes an actuator to counter the biasing force for disengaging the lock to permit longitudinal translation of the rotatable drive assembly via the knob locking assembly when disengaged.