If you have some form of knee pain, in the front of the knee, the issue might be just tight and weak glutes. Stretching the quadriceps and the calves might help but as Coach Mike Boyle pointed out many years ago - anterior knee pain is mostly tight glutes that lead to a tight IT band, and shows up as pain in the front of the knee.
The ideal solution is to see a good physical therapist. But I know that a lot of us are currently not in a place to see a physical therapist. Here's 2 things you can do to feel better immediately, assuming that's why your knee hurts.
Step 1: Release
Release the glutes with a lacrosse ball. A hard rubber ball or a hockey ball will work as well.
You can do this by lying down on top of the ball, or standing against the wall with the ball between you and the wall.
The first area to search for will be above where you'd normally sit, when you sit on the floor. And a little to the outside.
Sit on the ball. Relax. Breathe slow and deep into your belly. And allow the ball to sink into the meat. More. A little bit more.
Now, just slowly and patiently dig around and look for a spot that will make your face twitch and turn a wee bit weird. If you are not sure, that's not the spot.
Once you find that spot - about 15 wiggles, and then move on.
Don't do too much, or you will be a bit too sore tomorrow.
Step 2: Stretch
Stretch the external rotators out.
3 minutes per side, stretching the outside of the hips out. Breathing is key.
With every exhale, just reach a bit more forward.
Do this once or twice a day, and within a week, you should start to feel magically better. In addition, stretching the quadriceps and the calf is always a good idea.
I recommend finding about 3 spots per day for the glute release, and slowly expanding the area of search. Don't spend more than 30 seconds on a spot. Don't try to undo a lot of tightness with just one intense session of mashing. Slow, ease into it.
The more you can breathe and relax, the better the results you are gonna see.
Please note that this is one cause for knee pain, and the most common one I see when there's no injury present. This is not a cure-all for all forms of knee pain, nor do I know why your knee hurts.
But if it does and you've been neglecting it, here's something to try out.
Let me know how this worked out for you.