Pretty sure that anybody who's closely watched, or better yet, coached basketball for many years, has at least a couple of stories about players who suffered major knee injuries.
I have a couple that span the possibilities. About 10 years ago, watched a female who was very explosive blow up her ACL. She came back at about 85% a little over a year later. She was still good enough to play, but had lost the explosiveness that had made her a difference maker.
3 years ago, watched a very athletic 6'10" post blow up his ACL in mid-Jan. By the time practice started the following Oct., you would have never known he'd been injured. Was actually running and moving better than before his injury. I believe he's still playing in Australia these days. The point is, every knee injury and every person is different.
I guess if somebody is really looking for hope in the ability to come back from an ACL, we could look to Royce Lewis of the Twins, who is coming back his 2nd injury to the same knee and all reports indicate that he hasn't lost a thing.
Like I said, and I think we all know, every situation is different when it comes to knee injuries.