Trying not to soap box....
Part of rehab should have been extensive proprio and he/she should be working on this as part of their regular routine including working on developing proper stance and movement patterns that reinforce proper kenetic chain ( I still do 3 years now) Brace? why? I don't get why anyone who got their ACL replaced and did the rehab benefits from a brace??? Both my Dr and PT were dead set against using one. That's why you went through the surgery. I get it if you decided not to have the surgery for sure.
My 'bad' knee is definitely not as strong as my 'good' knee but it's defintiely getting there. my inner quad, the muscle right near the knee cap has pretty decent definition. aside from some cracking/stiffness and sometimes issue at full extension/hyperextension, my knee basically has no issues.
my doctor has me doing this straight leg decline for 10 seconds, 10 reps, 3 sets that is really helping my quads.
otherwise ive done less of the PT machines that i was doing as my doctor said doing the above was by far the most important thing for building muscle/improving atrophy.