I don't want to get you worried or anything,but that is what Hot Rod started doing. We didn't know that anything was wrong like that as we'd just taken him for his checkup in November. His surgery was March 31st. He went from a grade 1 to a grade in that time. He would not want to walk, he'd just stop, sometimes he'd sit down in the middle of the street.
You may or many not need to have surgery but it is best to get it checked out. He may be able to have physical therapy to help. I think it is best for be informed. Make sure that if and when you have surgery that your surgeon knows what he is doing. Ask how many surgeries of this nature that he's done and if you do not feel comfortable, please find one that you do feel comfortable with. If you need more info please feel free to pm me.
Hugs to you and your little one.