Depends if you have lost the stability it was providing. Where was the original graft taken from? You have already lost the sensory part that the original ACL was providing with the initial injury, so the only reason for another one would be loss of rotation stability in your normal/vocational activities.

It is possible that the tear was already there and was not the cause of the swelling during this recent episode. They should check the Wikipedia reference-linkmeniscus carefully as well