Ok, this guy’s knocked out some teeth here:
Danny Granger, American professional basketball player for the NBA’s Indiana Pacers, famously knocked out his two front teeth in a victorious game against the Boston Celtics on 1 November 2008. You can say both of these:
- He knocked out two teeth.
- He knocked two teeth out.
But you can only say one of these:
- He knocked out them.
- He knocked them out.
Compare: “knock out” is a phrasal verb like:
put away (aufräumen), bring up (=mention), try out, give up, call up, rip off (=steal), think over, boss around (herumkomandieren), make up (=invent)
They all use the structure of “knock it out.”
There are lots of lists and exercises here. Try them out!
Contrast regular two part verbs:
fall for, bump into, get over, look at, go up, fall down…
Look at them!