In the same position myself... I think it's quite common for the 'good' knee to worsen, after all, it's taking the strain for the bad one, doing way more work and absorbing more of those body stresses. Sod's Law....
As you say, no touching that one as long as you can - got to have one knee that vaguely works properly!!!
Take care Tinks, it'll get better in time, you're not alone lass.