I know several consultants who would agree that "prehabilitation" is just as important as rehabilitation. Your reluctance to attempt any exercises now doesn't bode well for if you do have the op as you need seriously high levels of motivation and commitment to progress with ACL rehab! Yes, pain needs to be controlled through analgesia but exercise can be graduated and slowly progressed, tailored to suit your level. Seeing a physiotherapist to get a professional re-assessment is required, I think. They can advise you on how to best strengthen your knee without stirring your symptoms up majorly, although I would add that initially, the exercises are bound to cause some discomfort/pain due to weakening of muscles, decreased balance etc. Knees crunch and creak a lot without major problems so I would not be too concerned about this, although sometimes difficult to ignore.

I was referred a patient several months ago who had been misdiagnosed 3 years ago and due to his age (80) was obviously too high a risk for surgical repair. He had a very lax ACL which I suspect was near enough a complete tear due to the laxity. It was giving way on a daily basis and made it difficult for him to walk around on the flat or down slopes. After starting him on a rehab programme and working on hamstring strength, quads and balance exercises (tailoring it specifically to what he needed), he was almost asymptomatic and found he could manage much better than previously. Obviously, this is different from your case but the point I am trying to make is that you'll never really know what your prognosis will be if you haven't given rehab a good go. Usually, conservative management is the first port of call unless otherwise indicated (i.e. high functioning athlete or severe loss of function/disability following injury). I would see a physiotherapist for their assessment and go from their advice, it probably won't do you any good "guessing" what exercises to do even on the advice of qualified professionals here, nothing can substitute a face-to-face objective assessment.

Hope this helps.