Greatings, I'm new to this forum and will give you my best opinion on how to strengthen your weak leg. I'm a nurse and have learned that the body has a very powerful homestatic ability in healing. What this means is, what is good for one leg is good for the other. In other words, you can strengthen the good leg and the weaker leg will get stronger and build muscle. You won't be off balance especially as the healing process continues. I realize that this may be hard to believe but studies have shown that even when in a cast, the weak leg can build muscle due to strength training on the non-injured side. What's ironic is that my wife just tore her ACL in competiion. She had surgery two days ago, and we are going to PT today. I will ask the physical therapist her opinion and let you know. Good luck.