A rotor blade and blade retention key assembly includes: a radially outer airfoil, a shank and a radially inner attachment dovetail. The attachment dovetail has a radially innermost surface formed with a notch at one axial end thereof, and a retention key is received in the notch, and rotatable from a retracted position where a retention key portion is substantially flush with the radially innermost surface, to an extended position where the retention key portion projects inwardly from said radially innermost surface and into a recess or pocket formed in a rotor wheel slot to prevent axial movement of the blade within the slot.