I never revealed how I was training to my surgeon of physical therapist. I figured it wasn't their concern; they had to heal the injured leg.
You can check my log I posted in your other thread for full on rundown of how I trained, but some good stuff is:
1 legged squats (stand on a plyobox with your uninjured leg so that you don't have to bend your injured leg.)
The curls and extensions you spoke of worked well.
I could eventually push a prowler VERY slowly with a focus on keeping weight on the uninjured leg.
I also did a LOT of ab and neck work (blast strap fallouts for abs allow you to take weight off the healing leg)
Oh yeah, also seated good mornings are your best friend. I worked them REAL heavy, like this