The word knowledge is non-countable a noun and does not have a plural form

Knowledge (like math), does not have a plural form in North American English. Knowledge is uncountable. However, I know in "Indian English" people say "homeworks". It's not wrong there, but my spell check is underlining it, because in North American English a lot of "school subjects" are uncountable nouns. "I take math classes" (literally "classes of math". I try to gain as much knowledge as I can. So knowledge doesn't have a plural form (like cattle). I mean you can USE it AS a plural, but it doesn't take on a new form. So short answer no. If you want one, you could use "expertise" or studies, or maybe competencies or skills, depending on the context.

"many disciplines of knowledge" can be applicable for your needs.