Not Cathe but...
I have knee issues, also. When I do squats I've found I don't have much trouble anymore if I 1) Focus real hard on making sure my weight stays in my heels,
2) Push my glutes (my butt) straight out and,
3) Make an effort to get LOW, really watching my thighs, trying to get them as close to parallel with the floor as I can.
These things all sound like they'd make knee pain worse but, surprisingly, the opposite has been true for me. Also, whenever you do forward LUNGES try lunging onto your 4" high step (no risers). I've found lunging forward onto the step instead of the floor really keeps my knees from going into a dangerous position. Of course, with dips (rear lunges) I just have to be focused and careful. Also, on lunges (forward and rear) I found that I was taking my rear leg too far out. As in all things, focus helps a lot. Finally, on cardio, I will do hops but I NEVER do jumps. Someone here suggested a while back that I forgo all blasts and do a treadmill run instead. On a treadmill I have more control over the impact my body receives. Since following this advice my knees are much better.