It could be panosteitis, although I haven't seen a small dog with it. It's usually a big guy thing. When Gris - Gris was little, she sprained her leg. The vet gave her two weeks rest and holistic anti inflammatories. I hate advising people on this kind of thing, because I know we are animal lovers, and it's hard to talk money, but I would consider what you wish to do with her, as far as running, sports etc. Like you said, you are not really attached now. I gave a couple of dogs back to a rescue, before I got my Whippies, because they were showing joint issues, and I wished to run with them. It's honestly part of the reason that I stayed away from larger dogs. Of coarse, mine could injure themselves now, and I could lose a running buddy. If you do bring her back to the breeder, their is a chance that she may put the dog to sleep, but I'm not saying not to do it, either. You paid for an animal, and now you face not being able to use it for what you want, and you face other bills. Orthopedics can be very expensive, so I can see why you may not want to start out that way. The rescue was mad, when I brought those dogs back. They felt like with me being a vet tech student, at the time, I should be willing to take on any animal, because of love alone. The truth is, if I could have ten dogs, and endless money, I could take on a potential hip dysplasia dog, and not feel strapped down, but my city limits me to three, and I need to make the best possible use of my situation, so I can empathize with what you are going through. It's a rough way to start.