I think my point may be missed. Activity level and ability to pull is not an indicator of joint health. You need to do radiographs (x-rays) to tell if a dog has the possibility of being dysplastic later in life. The surgeries to fix problems later on is crazy expensive, so I would not purchase a working dog like this without an OFA hip rating. I'm just trying to give you tips to protect your investment, because it's important that breeders you purchase your dogs from do these tests.
Also note that just because a parent is OFA good or excellent does not mean all the offspring will be. Occasionally a good dog will through puppies that have hip problems.
do you mush?