YOU SAID:

he’s been told he needs a knee replacement and had been waiting over a year

INTO JAPANESE

彼は膝の交換が必要だと言われ、1年以上待っていた

BACK INTO ENGLISH

He was told he needed a knee change and had been waiting for more than a year

INTO JAPANESE

彼は膝の変更が必要だと言われ、1年以上待っていた

BACK INTO ENGLISH

He was told he needed a knee change and had been waiting for more than a year