my knees get very very stiff and sore, just from sitting around. or if i work a long shift by the time i'm off i can barely walk because they're so stiff. my hips get sore if i walk a lot too lately.
one thing about calcium, even though you might be taking enough or getting lots in your diet, other nutrients can determine how much of it you actually absorb and use. magnesium is one, and protein is one, and i think there are more, possibly vitamin C (not too sure)
i take a calcium and magnesium supplement but i think that my problem is i don't get enough protein therefore i can't use all the calcium i get. if you work in a health food store you should access to some good vegan protein shakes. i'd be using them by now if i could afford to but i can't, hopefully you get a good discount
but i'd suggest taking some in soymilk every day for a week along with a cal-mag and see if it makes any difference.
also i was told that we lose more calcium at night so try to take calcium before bed.