I can happen, sure. Just that that is not the way to bet.
I’m asking if there are videos that show the actual effects of being knocked out, and not just videos showing somebody acquiring semi-lucidity and others proclaiming “Well, no harm done!”
I’m not sure of the point you are making, are you arguing that he did have brain damage despite a medical professional saying he didn’t?
How long ago did this happen?
Except that’s not what the OP was asking about. They didn’t ask about the aftereffects, just, “Can you knock someone out like that?”
Clearly, the answer to that is “Yes”. We have videos of it happening. What happens afterwards is outside the scope of the question.
In retrospect-true.
Minor quibble (not disagreement, but quibble). Such as in the pop-sci example I linked, the issue is that sure, it can be done. And in the anecdotes, it can sometimes happen with minimal side effects. But in some number of cases it happens it’s not that they’re knocked out, but that they’d be in a coma or dying which is admittedly a bit different than just being “knocked out”. Of course, that absolutely depends on how, where and how hard they were hit to induce that state, no argument.
Again, quibble, not disagreeing with your point.
My answers above were attempting address the OP directly. I do agree that if one were to sustain the type of injury that often happens in movies, there would be a high probability of TBI.
But that’s the movies. Even in dramas there a lot of things that would seriously injure a person, but doesn’t. Falling down elevator shafts, getting hit by cars, etc. But, again, it’s the movies, I think people are conditioned to accept a bit of dramatic hyperbole.
Oh, that’s darn certain, bad movie physics, biology, definitions of physical trauma and the like are rife. I couldn’t even guess how many threads we have on that. Especially when it comes to medical injuries from trauma, whether it is being shot, knocked down, knocked out, or what have you.
Of course, not if it was done by a “karate chop” 
My favourite was Bruce Willis in Die Hard falling one floor down a vent shaft then catching himslef on the opening to a air duct with his fingertips. (a) would just pull off those fingers (b) if he didn’t slice them off on sharp air duct metal edges.
it’s right up there with the trope when fighters beat the royal crap out of each other’s heads with punches and hits with solid objects, only to shake it off and keep fighting for several minutes.
“nice padded”? As I understand, pro gloves are not that soft -they are fairly solid. their main purpose is to stop the boxer (not the boxee) from damage; specifically, a good solid blow to the skull will just as likely (more likely) break bare knuckles.
the fact that a lot of boxing “almost” knockouts allow the person to get up within 10 seconds demonstrated how difficult it is to land a knockout blow.
I was kidding, sort of, and had Butterbean’s imposing figure in mine. It would suck to get knocked unconscious by a head strike of any kind but, if I had a pick a method, a quick ding on the button with a gloved fist would be up there.
Boxing gloves also weigh about a pound each.
I remember us 50’s kids calling it a “judo chop.” Or might have been early 60’s.
In my case it was the '60s. I wonder if those work IRL 
It was still used in professional wrestling, at least a bit, until at least the mid-80s. I remember a friend’s dad saying to the TV, “Give him a judo chop to the throat!”, and my buddy and me laughing at how ridiculous that was, until the announcer shouted, “And it’s a JUDO CHOP TO THE THROAT!!!”
Buddy’s dad was, of course, smug about it.
Which is just plain wrong. No chops in judo. No kicking or punching of any form.
The whole point of Judo is to create a sport where you can fight at 100% without one or both competitors being stretchered off, or worse. No techniques that bring about injury that can’t be referred in a safe manner. So standing work concentrates on throws, and ground work is essentially wrestling with the additional spice of strangles and arm locks. Very rare for serious injuries and essentially unheard of for fatal injuries. Those I knew who got injured were either silly bad luck (a thumb caught in just the wrong place and needing surgery) or being bloody minded and not taking the fall (thus losing the bout) and putting their arm down to the ground (shoulder dislocated).
We learnt to take falls. You can’t do the sport properly until you have an ingrained reflexive ability to breakfall. Relative to the thread, you learn from day one about protecting the head from striking the ground. Breakfalling is a very worthwhile skill.
I haven’t participated in Judo in a very long time, but I did it for a while after college, up to a blue belt (about 1/2 way to a black belt), and I can confirm this.
However, I can also confirm that kids in the 70s in the US referred to a open, side-hand strike as a “Judo chop” because we didn’t know what we were talking about.
I’m not even sure that in Karate, such a strike is called a “chop,” even when it is used to break boards in a demonstration. What did we know?
I wish this shorthand trope had never got started. It give people (me included, before I learned better) the belief that you can easily and routinely do this.
It became the driving action at least once in every Mannix episode. If Mannix were a real person, he’d be dead at 40 from CTE, not thanking Dr Sloan for his magical healing abilities. 
Just like the judo CHOP. There’s “shorthand” writing tricks to move the plot along (3 minute DNA results, for eample) and then there’s pure fantasy.
Please don’t tell me you can’t cure amnesia with another blow to the head. I don’t think I could take it.
Sometimes it did take Mannix a couple minutes to revive fully from being knocked unconscious (length of commercial break). He’d be sitting up on the exam table, maybe rubbing the back of his head but raring to go.
AIUI A blow to the head severe enough to cause unconsciousness usually causes some memory loss as well.
-When I came to in the ambulance, I had a vague memory of briefly lying in the street. I had no memory of being hit by the car. That memory has never returned. I don’t expect it to.
-In the movie Witch Hunt, Dennis Hopper’s character (non-spoiler) is rendered unconscious by a blow to the head. When he eventually regains consciousness, he has great pain in his head, no idea how long he has been out, and no memory of the blow. Being a detective, he us quickly able to deduce what happened. But IIRC that is the only way he knows.
-In some Dateline, or true crime special, a woman claimed that an intruder entered her home, killed her husband, and then knocked her out with a blow to the head. The cops immediately knew she was lying as she claimed to have perfect recollection of the moments before she was knocked out and to remember exactly when and how the intruder hit her. This is very nearly impossible.
-One of the episodes of Tales From The Darkside I like a lot ( I won’t give the title or spoil anything) unravels at the end. A character who is recounting events suddenly realizes that the way they explained things has to be wrong. For it to be right, the blow that knocked them out would have to have been from the front. They distinctly remembers being hit from behind. Again, this is massively unlikely. They would not remember at least several minutes before being knocked out. They could only know where on the head they were hit by checking where the pain, bruising, swelling etc were after they came to.
ETA-
Oops I forgot to address this. An episode of MASH has a very realistic depiction of amnesia. a bombadier learns that the last target he bombed was actually a village filled with innocent civilians. This makes him question how many other innocent people he may have killed. Unable to deal with things, his mind snaps. He forgets all details of his life and identity and believes he is Jesus Christ. Rather than a blow to the head or other quick cure, he is shipped back to the states to enter a mental hospital and a long time of therapy.