How I make knockdown system?

Hi, I am trying to make a knockdown system similar to a Sleeper Hit game called “Rogue Lineage”.

I really don’t know where to begin with so far since Devforums posts I checked are mostly ragdolls and so, so I am asking this there.

I’m here for answers.

You can disable the death state so the player doesn’t die when health reaches 0. Then detect if the health is below a certain point to ragdoll the player.