Runners knee not getting better?

Go to a running specialty store where you can talk with them about your shoes, insoles, etc. I'm not so sure that you have "runner's knee."

There can be multiple causes of knee pain. Iliotibial band syndrome is common for beginning runners (and is not "runner's knee"). But improper shoes can also do it. And the instability of too much cushion from shoes + treadmill can do it too.

How long you have to deal with this depends on what exactly "this" is. If/when you start up again, stick with walking for at least a couple months. In the meantime, you might try an exercise bike in order to strengthen the muscles that stabilize your knees.

I don't run on the treadmill but I've had an experience with runner's knee while running on the road. I was using Nike Frees 5.0 and my knees always bothered me while I ran. After lower body muscle strength workouts and correcting my running form, however, now I can run 5+ miles on the road without any joint pain. Try working on your running form and it might help you get rid of runner's knee which is unnecessary extra force on joints when you run.

I looked up videos on running form and running on the your forefoot or balls of your feet can help a lot. I don't know if this applies to treadmill running but it should be the same.

For now, rest a few days from running should help your knees recover. Correct your running form next time you run. Correcting running form is like breaking an old habit. It will be uncomfortable at first but after getting used to it and forcing your body to run correctly, you should be pain-free like me. Again, I've had this experience and fixed it on road running. Hopefully it applies also for the treadmill.

I had really bad runners knee while using Nike shoes with little support. Now I wear brooks with a medial post that supports my pronating ankles and have zero knee pain. Your shoe choice is very important go to a runner store and they'll suggest a good shoe to use and this should help your knees.