Probably been sat back on her bottom at some time; quite common when pushing back over grass. Does the plastic cap at the base of the rudder look new?
As long as the rudder moves full and free left to right on ground, and there's no sign of buckling in the elevators, you'll be fine. It's a very simple structure and won't be capable of hiding damage to any great extent. Have a look inside the hinge area with a strong torch if you like, you can see almost everything. Loose rivets can be another sign of damage, have a look for greasy stains around the heads.
Love the old 172, one of my favourite Cessnas.