With good form, your knees shouldn't be involved that much: https://exrx.net/WeightExercises/Quadriceps/BWSquat - your knees shouldn't go past your toes.

fwiw high weight + low reps (4-6) if you want to get stronger, lower weight with more reps for getting bigger (8-12)

Have you looked into isometric weight training? Heavier weight, lower reps, static holds for longer duration. Typically used in physio for rehabilitation but can also work as exercises on their own, especially when you get older and have joint issues.