I've been getting ready to teach a class by trying to explain to myself the difference between truth and knowledge from a Lacanian perspective. I've been at it for a bit now, and I want to write down what I believe I've worked out.
Knowledge is comprised of things we can say. It is the stuff we can speak or explain to ourselves and others. I can share knowledge, and others can share knowledge with me.
Empirical pursuits like Science produce knowledge.
The truth is outside of knowledge. It is what remains unsaid.
Even though we can't "speak the truth" (at least not all of it), it is good to try.