I believe the general description of "knock" refers to the sound: engines subject to "knock" make a lot of noise. Traditionally defined, "knock" is brought about by ignition of the fuel/air charge prior to TDC of the piston, however that happens. Whenever it happens, rapidly expanding, burning charge encounters a piston that is still moving toward TDC as a function of the momentum imparted by the crank and flywheel. This causes a confrontation between the rising piston/crank/flywheel assembly and the expanding charge wishing to drive the piston down; hence lots of things are driven into each other when they don't want to be, and noise and wear and damage result. Knocking, or pinging/pinking, can commonly happen in a spark-ignited crank piston engine when the timing is too far advanced, even though detonation does not occur. 

 "Detonation" essentially refers to things burning really fast, such that there is no flame front, or essentially no flame front. It happens in HCCI, and in "engine run-on" when ignition in a very hot crank-piston engine is turned off, especially when running on low-octane fuel. HCCI engines are often referred to as "knock engines" although they are actually not so, according to the definition above. That is, HCCI engines really do detonate, in that pretty much all of the micro-droplets of fuel in a homogeneous mixture combust nearly simultaneously, which is more than can be said for either SI or CIDI engines. But they do not "knock" unless this detonation happens prior to TDC. Actually, though, recall that knock as defined above really just means making a lot of noise. According to this definition, crank-piston HCCI engines also "knock," because, even when spontaneous ignition happens exactly at TDC (which it hardly ever does, by the way), the high peak pressures and energy release rates of HCCI tend to hammer the piston against connecting rod and crank, even when they are already moving downwards. They are simply not moving downward "fast enough," such that the piston is driven downward faster than it would "like" to be, thus again creating lots of wear and making lots of noise.  

 So get rid of the connecting rod and crank. Now, if the thing still detonates, which it will, on an HCCI model, as long as the charge is homogeneous and the compression pressure is sufficient to initiate spontaneous combustion, you have an engine running on detonation alone, without the phenomenon of "knock." I.e., run a double-acting free-piston HCCI engine and there is no such thing as knock, but lots of such thing as detonation. Run it as rich as you want as rich as stoich will let you. It doesn't make lots of  noise, because there are no connecting rods and no crank to oppose the piston motion. It wants to move extremely rapidly in a direction opposite to that which caused the compression; OK, go for it. There's nothing stopping you. No noise, no knock. Total detonation. It has been built in the past, and it worked exactly as described. It is presently being built again, and it will once again work exactly as described. It's exactly the same thing as a pulse-detonation jet engine, only smarter and incomparably cheaper and more reliable. So there. No references; don't need 'em. References are for people who don't have confidence in what they are talking about. I am not one of those people. 
 66.80.111.18