Does publishing in a journal and getting cited constitute a "contribution to knowledge"? If I publish my research in a respected journal and I get cited a few times in less than a year (cited as part of the literature review and background of my field), does this mean my work is a "contribution to knowledge"?
What journal?

In principle, regardless of citations, anything accepted to be published in a journal should be a contribution of knowledge. There are some exceptions to this, like survey papers, but for the most part publications should have a novel contribution.

The citations help measure the impact of the contribution i.e. how relevant or useful it is in the field. But an uncited, published paper should still contribute knowledge.

And, of course, if it was published in a predatory journal, it may not contain a knowledge contribution. Citations make this less likely, unless the citing papers themselves are also in predato journals.