Hurt my knees- exercises to help?

So my knees are really bothering me, and I’ve had to put the breaks on any form of hiit or any jumping at all. Even going up and down my stairs hurts. I’m wondering if it’s tendonitis- been icing my knees frequently. Does anyone know of any good exercises for the knees, or things to do to help the healing process?

I am going in for a physical in about a week- definitely going to have the doctor check my knees. Very frustrating. Trying to take my own advice to Korse yesterday and focus on what I CAN do instead of what I can’t. But man, I love hiit!