Konnichiwa!
You mentioned a very delicate point about that idiom, so please pay attention:
Standing on the "knees" is actually not correct!! There're 2 idioms similar to this in the English language:
1) stand on one's (own) two feet
It means to act in an independent and forthright manner.
For example: I can stand on my own two feet without any help from you!
2) bring (someone or something) to its/their knees
It means to have a negative effect, or destroy someone or a group of people, to defeat someone/something.
For example: He brought them to their knees by answering all of their questions.
He was brought to his knees by the betrayal of his companions.
The death of his son brought him to his knees.
Both of the two idioms above, have equivalents in the Farsi language with the exact words as above and the same meanings!!! Look:
1) روی پاهای خود ایستادن
It means as the same in number 1.
2) کسی (یا چیزی) را به زانو در آوردن
It means as the same in number 2.
Sayonara! ^^