Guru, I'm not sure I would classify my awareness of my own interior state as 'knowledge' ... certainly not, as you say, the same kind of knowledge that I acquire through my senses. My own self is something that I experience ... and in fact I am the only one who can experience it.
There is some overlap though in that once I've acquired knowledge, it becomes part of my intererior state and I know that I know something. I experience my knowledge of it, but again I am the only person who can experience that. No one else can know what it is that I know unless I impart my knowledge to them in a way that they can receive through their senses.
In fact you don't know that you are talking on a messageboard.
You don't know that until someone answers your post ... makes their awareness of your internal state available back to you through your senses. And ... a certain class of 19th century philosophers would say that even then you don't know it because you have no way of confirming the existence of the person who responds to you except by your own senses which might be deceived.
I wouldn't like to take it that far - I'm too much a pragmatist - but I would say that the responses you receive only increase your confidence that if you continue posting on the messageboard you will continue to receive a response. So the world accessible to your senses behaves as if it were really out there whether it really is or not. Your experience is consistent and predictable ... like the experience of time and gravity, but there is no way to assign a certainty of existence to any of these things.
Jn