A hand-held surgical instrument , comprising: a handle assembly ; a shaft portion having a proximal end portion and a distal end portion ; a knob housing coupled between the proximal end portion of the shaft portion and the handle assembly ; an articulation lever rotationally coupled to the knob housing ; a cam plate non-rotationally coupled to the articulation lever and disposed within the knob housing , the cam plate defining a notch therein; a slider supported in the knob housing and configured to translate within and relative to the knob housing between a proximal position and a distal position; and a surgical loading unit having a proximal body portion configured to detachably couple to the distal end portion of the shaft portion , and an end effector pivotably coupled to the proximal body portion, characterised in that : the slider has a tab configured for receipt in the notch of the cam plate when the slider is in the distal position to prevent rotation of the cam plate; and the cam plate is configured to operably couple to the end effector such that the end effector articulates relative to the proximal body portion in response to a rotation of the cam plate, wherein the surgical loading unit is configured to move the slider toward the proximal position upon assembling the surgical loading unit to the distal end portion of the shaft portion . a handle assembly ; a shaft portion having a proximal end portion and a distal end portion ; a knob housing coupled between the proximal end portion of the shaft portion and the handle assembly ; an articulation lever rotationally coupled to the knob housing ; a cam plate non-rotationally coupled to the articulation lever and disposed within the knob housing , the cam plate defining a notch therein; a slider supported in the knob housing and configured to translate within and relative to the knob housing between a proximal position and a distal position; and a surgical loading unit having a proximal body portion configured to detachably couple to the distal end portion of the shaft portion , and an end effector pivotably coupled to the proximal body portion, characterised in that : the slider has a tab configured for receipt in the notch of the cam plate when the slider is in the distal position to prevent rotation of the cam plate; and the cam plate is configured to operably couple to the end effector such that the end effector articulates relative to the proximal body portion in response to a rotation of the cam plate, wherein the surgical loading unit is configured to move the slider toward the proximal position upon assembling the surgical loading unit to the distal end portion of the shaft portion . the slider has a tab configured for receipt in the notch of the cam plate when the slider is in the distal position to prevent rotation of the cam plate; and the cam plate is configured to operably couple to the end effector such that the end effector articulates relative to the proximal body portion in response to a rotation of the cam plate, wherein the surgical loading unit is configured to move the slider toward the proximal position upon assembling the surgical loading unit to the distal end portion of the shaft portion . <EOS>