I have a little poodle (3lbs) that has luxating patellas in both back legs.
The vet told me to watch his weight and that as long as he was not overweight he would probably never need surgery, the cost of surgery should he need it is 2500 per knee. I worried about this for a long time, but he is six years old now and I don't worry about him anymore, he doesn't seem to have pain unless we go for too long walks, and now he walks about a half a block and I carry him for a bit and then he walks and bit further and I pick him up again, he lets me know when to pick him up, he justs sits down and doesn't move. He has good days and bad days too just as another post said, sometimes he runs and plays and you would never know he has a problem.
Enjoy your baby and try not to worry, it may never happen.