You floated dropping "maybe even the back squat." It's a great lift, but the bar-on-back position loads the low back and demands more hip/ankle mobility; under heavy fatigue it's a common tweak source. For your goals (function, knees, longevity) we lead with squat patterns that are kinder to the spine and better for the knees.
What replaces it
Main bilateral squat → Front Squat (upright torso, less low-back load, big core + mobility)
Unilateral quads + knee health → ATG Split Squat and Bulgarian Split Squat