I don't see any motorcycle on top of any ankle. It looks like someone wedging his foot under a parked vehicle.
The guy starts out with one leg in front of the front wheel, then it changes to the other leg in a different position, and then he's flipped to his backside; very confusing.
Also, the cop is walking, not even riding. I don't see how he could even knock someone down with that lack of momentum.
To be honest, I've never seen a man react that way and so loudly without suffering severe life-threatening injuries or burns.