Truth is a completely objective concept. It exists entirely separate from knowledge. For example, it is true that there are other solar systems. However, for a long part of our history, nobody had any knowledge of these solar systems. Also, knowledge can be subjective and is ever changing. In the scientific community, we accumulate more facts everyday which shape our understanding of knowledge.
Truth is what is factual. It remains the same whether or not one person, or anyone at all, knows it. Knowledge refers to what is known, either by one person, a group of people, or all of humanity. They intersect, but knowledge and truth are the same thing. It is a noble goal to attempt to expand knowledge to include more of truth.
People may have knowledge, but that does not mean that it is all factual. Knowledge is by definition "information and skills acquired through experience or education; the theoretical or practical understanding of a subject." (dictionary.Com) Nowhere in this definition states that knowledge is truth. It is simply what we know according to previous experience, which could have a skewed point of view.
Knowledge concerns how much you know, not how truthful you are. I could have knowledge of an ongoing crime, yet lie to the police and tell them I know nothing. Knowledge is the challenges we face every day. How familiar we are with our surroundings. How much we have learned in our life. Truth is knowing right from wrong.