I tell you, honestly, the only time I get lower back pains is when I stop deadlifting, a month without deadlifting and my lower back
is at me.
Squatting is bad for your knees if you dont go at least parallel, I think if you do quarter reps the knees will take the brunt of it, below parallel
its the glutes and hams, could be wrong though but I ve never had knee issues.