osteoarthritis and knee buckling

I have been diagnosed with osteo in all three compartments of both knees.  I also have baker's cysts in both knees.  I am used to the pain of bone on bone but experienced something new last night and today.  Felt a sharp stabbing pain in the back and side of my right knee which is constantly swollen.  Then my knee gave out.  This happened quite a few times last night.  I got up this am and went downstairs and nearly fell since the same thing happened again.  I was too afraid to drive to work so I stayed home and attempted to make an appointment with my rheumotologist and ortho doc, both of whom could not see me till later this week.  My knee is no longer buckling but I still am getting some twinges of sharp stabbing pain which is very quick and then leaves.

These are very new symptoms and I am wondering what is going on. 

I'm sort of new to the whole OA scene, but - my issues is my hip, and sometimes I feel my hip feeling as if it's going to buckle. It's like I'll randomly have a "buckling" day, which doesn't always correspond to a "severe pain" day - and then I'll be fine for a while, then maybe another buckling day or two...
Anyway, I hope you get some relief from it. Such a weird and unnerving feeling!