Your achy knees while running may be due to weak hips. Strengthen the hips and running may be enjoyable again...not too mention much smaller hips:) - Good to keep tucked away in case I need it.
Wide Squat This relaxing stretch targets both hips at once while opening up your lower back. Stand with your feet slightly wider than your hips. Bend your knees and lower your hips down toward the ground. If your heels don't touch the ground, roll up a towel or the back of your mat and place it under your heels for support.
For my hips! - started running again now that it's warm out which means tight hips! Hope these stretches help!
Running Stretches For Tight Hamstrings and Hips