YOU SAID:

I collapsed to my knees, knocking my head painfully against the chair.

INTO JAPANESE

私は膝に倒れ、椅子に頭を痛めつけました。

BACK INTO ENGLISH

I fell down on the knee and hurt my head on the chair.

INTO JAPANESE

私は膝の上に落ちて、私の頭を椅子に傷つけました。

BACK INTO ENGLISH

I fell on my knees and hurt my head to the chair.

INTO JAPANESE

私は膝の上に落ちて、私の頭を椅子に傷つけました。

BACK INTO ENGLISH

I fell on my knees and hurt my head to the chair.