first off a more important and fundamental question is needed to be answered. and that is "what exactly is power?"
some definitions state that its the rate at wheich energy is being used. some say that its the mount of influence or authority a thing has.
in philosophical use i think that complete power is complete free will. and so therefore power is the amount of free will you have.
and someone with complete power will be able to do anything and he will therefore he will see the world/universe as a blank canvas where he can create his own rules.
a person with complete power wouldnt have knowledge of gravity or any laws of physics becuse if he did then hed be restricted to making everything being effected by gravity.
a person with complete power would have a completely empty mind so no i dont think knowledge is power.
but another important question is "why did people say that 'knowledge is power'?"