Fitness

I recommend browsing videos from Squat University on Instagram and seeing if you can identify the specific type and cause of knee pain and rehabbing that before you write it off as "part of aging".

I spent a lot of time in physical therapy recovering from a broken femur this year. One exercise they had me do to get the strength back in my knee was to do squats with an exercise ball behind my back leaning against a wall. This took some of the strain off while allowing me to get pretty far down without fear of not being able to get back up. This might be helpful for you as well.

Perhaps Bulgarian split squats or Barbell reverse lunges?

Spend some time on knee health, look into knees over toes guy. You might have some muscle imbalances, find a unilatetal program.

Maybe step ups, or lunges.

You might try knee sleeves. They helped me a lot.

Generally speaking, without assessing you.....add tke's and Nordic hamstring curls to your routine during the first part.

Move squats to the latter 3rd of your workout.

Do that for 12 weeks and you should notice a difference.

How old are you? Improper use is the enemy here, not disuse. Just manage your load so it doesn't hurt and your knees will improve