I am doing PT right now for the stiffness (no or rare pain) of my lumbar stenosis. As @cathykar said, my pt has been pelvic tilts, single bent knee raises, slow bent legs side to side (stretches), core strengthening, bridges, step ups, walking, seated cat/cow (my knee implants don't like the kneeling version), and daily water workouts using an aqua jogger belt in deep water. Interestingly, I have done all of the above exercises most of my life, but this PT person has me doing almost all of them a bit differently, which has made a big difference. It might be worth it to have a few PT sessions so the exercises are tailored to your specific stenosis.
Stuart McGill is a noted ortho MD expert who wrote most of the textbooks used to train PTherapists. He has a lot of good videos on youtube.