I find that a knee flexion movement is useful for maintaining my knees in a relative pain-free state. I use a band for leg curls, though, and they are kind of a partial movement, due to the nature of the bands, and the limited equipment in my home gym.
I have also found that tractioning out the knees with a jumpstretch band seems to help provide some relief from the low-grade continual ache as well. Basically this is just looping a band around your ankle and stretching the band out until there is a significant amount of pull on your knee, then you slowly move and twist your knee. The JS band people (Dick Hartzell and company) insist that doing this improves blood flow and helps open up the joint space, albeit minutely, to provide relief. This works well for me, and it works especially well if I do it every day.
While you have the bands out, go ahead and try some TKE's with the band.
If one of your problems with your knees is a weak VMO, then TKEs are definitely one of the things that help solve that problem.