An adapter assembly for selectively interconnecting a surgical loading unit and a handle assembly having at least one rotatable drive shaft, the adapter assembly comprising: a knob housing configured and adapted for selective connection to a handle assembly, the knob housing including a drive coupling housing; and at least one drive converter assembly for interconnecting a respective one of the at least one rotatable drive shaft and a portion of a surgical loading unit, wherein the at least one drive converter assembly is adapted to convert and transmit a rotation of the rotatable drive shaft to an axial translation of at least one axially translatable drive member of the loading unit, wherein the at least one drive converter assembly includes a first drive converter assembly including: a drive element rotatably supported in the knob housing, wherein a proximal end of the drive element is engagable with the rotatable drive shaft, and wherein the drive element defines a longitudinal axis between proximal and distal ends of the drive element; a drive nut threadably engaged with a distal portion of the drive element; and a distal drive member, a proximal portion of the distal drive member being disposed in mechanical cooperation with the drive nut, a distal portion of the distal drive member configured for selective engagement with the at least one axially translatable drive member of the loading unit; wherein rotation of the rotatable drive shaft results in rotation of the drive element, and wherein rotation of the drive element results in axial translation of the drive nut, the distal drive member, and the at least one axially translatable drive member of the loading unit; wherein the drive nut is disposed about the longitudinal axis, and the distal drive member is disposed along the longitudinal axis; characterised in that a radial center of each of the drive element, the drive nut, and the distal drive member is disposed on the longitudinal axis; and wherein the entire lengths of each of the drive element, the drive nut, and the distal drive member are coaxial with one another. a knob housing configured and adapted for selective connection to a handle assembly, the knob housing including a drive coupling housing; and at least one drive converter assembly for interconnecting a respective one of the at least one rotatable drive shaft and a portion of a surgical loading unit, wherein the at least one drive converter assembly is adapted to convert and transmit a rotation of the rotatable drive shaft to an axial translation of at least one axially translatable drive member of the loading unit, wherein the at least one drive converter assembly includes a first drive converter assembly including: a drive element rotatably supported in the knob housing, wherein a proximal end of the drive element is engagable with the rotatable drive shaft, and wherein the drive element defines a longitudinal axis between proximal and distal ends of the drive element; a drive nut threadably engaged with a distal portion of the drive element; and a distal drive member, a proximal portion of the distal drive member being disposed in mechanical cooperation with the drive nut, a distal portion of the distal drive member configured for selective engagement with the at least one axially translatable drive member of the loading unit; wherein rotation of the rotatable drive shaft results in rotation of the drive element, and wherein rotation of the drive element results in axial translation of the drive nut, the distal drive member, and the at least one axially translatable drive member of the loading unit; wherein the drive nut is disposed about the longitudinal axis, and the distal drive member is disposed along the longitudinal axis; characterised in that a radial center of each of the drive element, the drive nut, and the distal drive member is disposed on the longitudinal axis; and wherein the entire lengths of each of the drive element, the drive nut, and the distal drive member are coaxial with one another.