The PT on youtube said that most PTs do concentrate on the quads and he said that actually puts more pressure on the knees and makes things worse. I have been working on my glutes for about 3 months now and see a lot of improvement and less pain. Here is the PT I follow on youtube. He has many videos. I am sold on strengthening glutes and not quads. If you are preparing for surgery then quads need to be strengthened because they are going to cut that muscle. Most doctors do not emphasize working the glutes, but it sure has helped me. Here is the link: