To throw out one's back

[rezaaa]

Why is the phrasal verb "throw out" being used in the expression to mean to injure?

 

[Skrej]

To begin with, remember that phrasal verbs are idiomatic. Idioms don't always have a logical reason or explanation behind them. Also, like many phrasal verbs, 'throw out' has multiple definitions and meanings. One of them (taken from the dictionary definition if you simply google the term) is:

twist, strain, or dislocate a joint or other body part. "He threw out his back at the gym."

 

[SoothingDave]

Probably from "out of alignment" or "out of position."

 

[emsr2d2]

Why is the phrasal verb "throw out" [STRIKE]being[/STRIKE] used in the expression "to throw out one's back" to mean "to injure"?

Note my changes above. Please make sure you put the whole phrase/sentence you're asking about in the main body of the post, not just in the title.