I got my last dog from the local dog pound. I am constantly getting comments on how awesome she is and how they wish that their dog was like mine. She is an awesome dog, but she surely did NOT start out that way!
Behaviorally, if you want to put in the time and effort, you too can have a dog like that. Lots of people get hung up on the dog's history and continue to live in the past. But don't let that common thought process stop you from getting a dog no matter the behavior problems- as long as it is healthy and as long as you are willing to take the time to train it.
Medically, there isn't a lot you can do about that. Many pound puppies will have some kind of long-term medical problem, so you would have to deal with that. I would say most of the dogs have had a very poor diet and that contributes to poorly developed bones, hips, and such. You may want to have a vet do a full evaluation before adopting.
The dog I have now, Waffles, has very bad hips and a deformed back. She probably won't live past 10 and our activities have been limited since she was 6-years-old. If you are a couch potato, then having a crippled dog may not be a big deal, but if you are inclined to go skijoring, play flyball, or compete in agility, be aware that not having a documented, well-known history of the dog will not put the odds in your favor.