Yes Pano is normally seen in larger breeds but it can pop up in APBT
's. I would put the dog on lower protein and maybe switch to an adult food if it is a pup eating puppy food.
There are a lot of food you can put a pup on that are lower in protein but still be a good diet. Deb might have other suggestions but I know the puppy food I feed has 28% (kirkland chicken and rice from costco) and the adult has 26% and that is pretty low.
If the dog has to eat grain free it is just a matter of looking at labels and finding one that will work. I am not into some of the foods with really high protein levels I like them a little lower and not over 30% but that is JMO.
I had a pup who was knuckling over in the front from too much protein and her ligaments grew too fast. I had to put her on adult food and put leg supports on but after 4 weeks of being on the 26% food she went back to normal. No long term effect she is a great working dog.
Hope that helps