To my knowledge, no issues with the knees (seem to be fine in exams, no history of injury).

I should have added to my original post (figures I'd forget something major, dur!!) that in the last few months, something that is new with this feeling I'm having is a "rotation" feeling. Hard to explain, not vertigo, no nausea. I just feel as though my body's doing a slow rotation from left to right. Like one of those ballerinas that turns ever so slowly on a music box. I'm rotating (or so it feels) clockwise (left to right). Doesn't always happen, more so when I'm tired/lacking sleep/overworked.

MS is fun times.