If you can Squat unweighted, at least do that, or if you can, potentially work upto a point where you just start feeling it, by doing a couple of reps with light weight and assuming that feels good, start adding a little bit more each time and then when you start feeling it a bit, train just below that level, so you're working just within the limit of tolerance, not beyond it, so each time you add a little more weight and do those 2 test reps, you're ascertaining tolerance level.
If you're not able to do unweighted Squats right now, go on Leg extensions, do a couple of unweighted reps and repeat the methodology I just described for Squats, by using a little bit of weight and adding a little bit each time, doing a couple of test the water reps each time, until tolerance is ascertained, then work within it.
Whichever exercise you do, go back next time and add a little more weight to the previous sessions limit and if you start feeling it, use the previous weight level you used. If the new level feels tolerable, add a bit more again, so each session you're basically reassessing where your tolerance level is, so you're keeping up with the healing process each time.
If you chose extensions, after 2-3 weeks, test yourself out again with Squats and see if you're capable of minimal Squat levels and if so revert back to Squats, otherwise continue the suck it and see process on extensions for another 2-3 weeks, then re-evaluate the Squats situation again.
Hopefully that all makes sense