OP I have a torn medial tear of my meniscus due to years of sports and running.
I haven't had mine surgically repaired however it was recommended by my doctor not to do heavy squats as well as this causes excessive compression of the meniscus.

I inlisted the services of a certified strength and conditioning coach to help me with proper form and help me regain range of motion. I no longer go past parallel when doing this exercise but after 6 months of proper lifitng technique I'm happy to report that I can lift 325LBS 10 times without issue (far cry from what I used to lift but I will take it) So to answer your question, yes you can perform squats with proper mechinics. I highly suggest working with someone to help you through your situtiation. Feel free to direct message me if you have specific questions.

not directly relevant as I've never done loaded squats, but in my day I was leg pressing 240kg.
I played a good level of competitive squash, and golf, and as a result of a combination of getting a bit overweight & both full flexing and rotating my knee joint I ended up with a meniscus tear and general degradation and eventually had to have an arthroscopy to clear all the debris from the joint.
The surgeon discouraged me from leg presses on the basis of the full flexing of the joint, which I guess is what you're hearing about flexing beyond 90 dgs in a squat, as it invites the possibility of more tear, and will exacerbate any existing meniscus degradation which leads to irreversible osteoarthritis.
Osteoarthritis, for those who don't know is where joint bones rub together when flexed because there is little or no cartilage between the bones to protect them from each other, and the bones grind each other down.
After my surgery and 3 months careful recuperation as prescribed I resumed normal life but pretty soon after my joint pain (through a degree of osteoarthritis) returned.
I consulted the surgeon again & he advised absolutely no full flexing (over 90dg) of the joint and no 'trauma' which included running, golf was still a bit painful too so I drastically cut that down too.
He also advised weight loss, simply to put less burden on the joint, which was a major factor in starting my journey on here, and I have to say that since losing some weight the joint does feel generally much happier.

Once meniscus damage, and the resultant osteoarthritis becomes too bad it's a one way street to full knee replacement; no technology exists to repair or replace cartilage. There are a few injections which are promoted which have mixed reviews at best but in reality the damage is irreversible. I researched that a lot, it's fully effective in more than 50% of cases and much greater in terms of people who are much happier.
And, a prosthetist advised me to have a full replacement sooner rather than later as compensating for the pain in one knee causes trauma in the other knee and you'll end up needing both replaced.

So, I quit the gym, quit golf, and lost weight. I walk at least 4 miles every day and do some basic body resistance workout routines at home, including 90 dg squats, 4x25 3 times a week and can report that my joint is 'happy'.

hope this all helps, good luck.

Thanks for this post, and the responses. I tore mine when I was 16, and don't know if the tear was repaired or removed. I am 34 now.

Deadlifts (classical) killed my knee after a certain weight. Basically now I try to remain aware of weight, and reps, with squats, deads, lunges, etc.

What I wonder is for those of us who watch both reps (not too much volume to overly tax the knee) and weight load, is there any chance of linear progression?

I've shifted focus to progression on upper body but wonder if lack of progression on my lower body impedes progress for weight loss, muscular sustainment as I age, etc.