My own Metric

I give one point for each.  Scale ends up being 1-10 this way.  It's never a zero.

Lateral (split between Tibial and Femoral so each location gets .5)
Medial (Tibial/Femoral again split same as above)
Patellar
Bakers Cyst
General Edema
Stiffness
General OA Achy Joint

Then it's +1 for any sort or worry or thoughts...
+2 if I act on any of that worry.  So for example.  I add one point I think about pain and add two points if I cut short a shopping trip because of it.  Tears are an automatic 2 points.

Currently I'm a 7 with both tibial and femoral lateral pain, patella pain, bakers cyst pain, edema, stiffness and tears.  Lots and lots of tears today.

It's amazing to me how many different ways my knee hurts me.  Intensity should probably be a consideration but I think I capture that with +1 and +2.  This works for me.  I'm hoping shortly to be back down to 4 or hopefully even a 3!  I expect the stiffness to fade, the lateral pain to ease off and if I don't hurt I don't think about it so those three points go too.

Still waiting for the Synvisc to kick in and trying not to fret that it hasn't yet.