When can I start squats given weak lower body

I(54M) have really fucked up knees. Like 5 surgeries (including an open reconstruction) fucked up. Like, can’t go down stairs without a railing fucked up.

My current goal is to do a squat with an unloaded bar ball. I can do 3x10x12.5 leg extensions (per side) and 3x10x40 leg curls (per side). My quads are the limiter on my glute kickbacks to 3x10x50.

I’m 6 foot even and 192 lbs. I only started doing leg days a month ago because I’ve always been afraid of a knee exploding but I can’t stand not being able to go down stairs.

Can I start squats now or do I need to build more strength through isolation exercises? Any hints, tips, suggestions are appreciated! Thanks for reading a long post!