I dunno what glucoseamine sulphate is but I had pretty bad knees which after weeks of trying to sort them out came down to me having tight hamstrings which screwed up the ligaments atached to my knees. this is apparently quite common with people who sit down all day in an office or driving or whatever.
The answer is to stretch your hamstrings every day. Only takes a couple of minutes, I do the lying down stretches.
HTH
Ok I'll try that, thanks.

that 'ache' is your ligaments over tensing. look forward to having a knee operation at about 40.

glucoseamine sulphate should prevent that.
better just comment on this- sitting cross legged can put the ligaments (and other soft tissues) under strain. The pain can be avoided by moving regularly and even better by not sitting cross legged. Even if you dont it is doubtful if you will need an operation by 40.
Glucosamine sulphate will not prevent posturally induced pain. There is however growing evidence that it slows the onset of osteoarthritis which is related to more impact related "wear and tear". I take this daily( although it is a case of shutting the stable door etc as I am having yet another knee op at midday tommorw)
Tight hamstrings can indeed be associated with knee pain ( and indeed back pain), however not normally with a cross legged posture.
I would be very wary of any forum/online/friend diagnosis (including mine) and would reccomend that you got an an appointment with a physiotherapist through your gp so that you can have a full assessment.