Most physicians will not give a definitive answer since it is too hard to predict. I would say 6-8 wks after surgery you should be at 50%. That being said, you really have to listen to your body. Try and build up to your prior regimen and be realistic about getting back to your pre-operative form. As far as risk of reinjury, anytime you have this type of injury you are always at a greater risk than the average person.
Everything in moderation
