If you're having knee pain with going up the stairs, there's an easy change to how you do it that will make your knees feel better.
To go up the stairs in the most energy-efficient way, your body wants to put its weight over your foot so your knee is forward in front of your toes but that puts a lot of strain on the back of the kneecap.
If you can just shift your hips back to get your shin vertical, then push up in that position, your knee will feel a whole lot better. The problem is that every time you land, you're going to have to recheck yourself.
I know that you're not going to do this every single time but if your knees are really achy, this is a nice way to make them feel better to be able to go up the stairs without pain.