Yep - Deered got it right - this is a case of hip dysplasia. (email me at firstname.lastname@example.org and I'll get your mailing addy and get your fabulous prize off to you!
BTW - from now on, if there is no correct answer posted, EVERYONE that put SOMETHING in the comments will be eligible for the prize, to determined by random drawing. So please - even if you don't have a clue, put something funny that makes me laugh :).
Here's a close up of the hip joint. Do you see how instead of two bones that look like they were made for each other, instead they look like they came out of a random grab bag from two different animals? Not good.
Even though one side is more affected than the other, both sides are affected.
Hip dysplasia is a multifactoral disease. Prevention is not as easy as not exercising your young dog, or buying a dog that has been "certified", or feeding it "right". In my family we have 3 dogs, 2 of which are breeds that are at high risk for this disease. The German Shepherd came from a non-certified, backyard bred, chosen-based-on-price situation.......If she hadn't been radiographed (x-rayed) for an unrelated situation (broken pelvis) we would have never known she has a slight degree of hip dysplasia (meaning that the ball and socket joint weren't perfectly a match for each other). It will probably never cause her any problems for her - it's an "incidental" finding that will most likely stay "sub-clinical". Let's take the Golden Retriever now......Specifically purchased from a breeder who has "certified" dogs, a low incidence of the disease, and a provision in the contract for a replacement pup if it's diagnosed etc. We fed him the "right" large breed puppy food, didn't let him heavily exercise, and didn't neuter until after a year. Guess who got diagnosed with hip dysplasia? That's his hip radiographs that were used for his case. It's not a subtle case either - it's definitely clinical and absolutely affects his quality of life.
So what can you do?
1. Genetics plays a role. But it's not as simple as buying a puppy from parents whose hips look good. Remember that there seems to be a lot of different factors that interact. There's definitely a breed association (and thus a genetic association) - if you are truly concerned about hip dysplasia, avoid buying from those breeds, or a mix breed that resembles that breed.
Want to know the difference between a pure bred dog and a mutt? When a purebeed or a mutt that looks significantly like a certain breed walks in the clinic, I have a list of differentials what is wrong. When a mutt walks into the clinic I have to do more testing to have a list of differentials what is wrong. Mutts are not necessarily immune to "all those purebred diseases".
2. There may be an association between sex of the dog and whether they develop hip dysplasia. Of course, by getting a female, you may be reducing your chances of hip dysplasia but increasing your chances of some types of cancer (remember that there are tradeoffs to everything - just like the purebred versus mutt argument).
3. There may be an association between when you neuter, and the development of hip dysplasia. Wait until after puberty (usually considered neutering after 1 year of age) and you may decrease your risk of hip dysplasia and other musculoskeletal disorders. This is one preventative strategy that I don't see a significant trade off - I think there are very few arguments related to the health of the animal that support altering/neutering before puberty.
4. Exercising and feeding? I think it's unknown at this point what the exact association is between these factors and hip dysplasia is, however appropriate exercise and nutrition intake seems to be preventative for a lot of general musculoskeletal problems .
I think appropriate nutrition is something that most dog owners have a handle on - and the specifics of what you might consider "appropriate" nutrition is a nuanced issue beyond the scope of this post. Sufficient to say that with the majority of the food on the market meeting minimum AAFCO standards and the information available out there with a simple google search, that as long as you aren't doing something totally weird with the diet of your large breed growing puppy (and if you are doing an alternative diet, you are doing your own basic research) than nutrition probably isn't a huge factor in hip dysplasia development.
What about exercise? I think that there is a credible link between "excessive" exercise and damage to growing bones (like nutrition - more general musculoskeletal stuff, not sure of any specific association between hip dysplasia and exercise) especially when you look at young horses. Does no "excessive" exercise means not allowing your growing puppy to run around your 5 acre property? How about the dog park? Going on walks? Running with me? Hiking? Swimming? Does it matter whether it's an on leash or off leash activity? When I was deciding what the appropriate exercise was for my growing Brittany puppy (Tess) I used the most current thoughts in horse/foal management. It's not that young growing animals shouldn't be allowed to run around at top speed - putting a young foal in a stall or a small pen doesn't allow their bones and joints to develop normally. The most current recommendations for foals that I've seen is that they should be allowed enough space to run around at will and "self-exercise" in an enclosure big enough that they aren't having to do frequent stops and turns dictated by a fence line. It's not the exercise/movement that's the issue - it's the addition of weight, an enforced/maintained speed, that continues until some outside authority decrees that the movement should stop. So, my interpretation of what was appropriate exercise for my puppy was this:
1. exercise stayed far below her fatigue level and attention span (thus on-leash walks, or agility training that focused on mental prep were OK), OR
2. exercise allowed her to choose the speed and duration of the activity. This included off leash play, dog parks, or slowish short runs/horse rides that took place over a small area (laps) where she could take a break when she wanted - she didn't feel compelled to follow me or keep a certain speed to "keep up".
Types of exercise I didn't feel like were appropriate was on-leash runs, runs/rides that were about speed and distance that had me "traveling" somewhere, bike rides, long hikes, agility obstacles such as jumps/poles, etc. These activities I saved until she was a year old.
Bottom Line: There are no guarantees when it comes to dogs and hip dysplasia. Multifactorial means that it isn't simple. The best way to prevent having to deal with this disease is to pick a breed that has a lower incidence rate of the disease. Of course every set of genetics that make up a certain breed or look of dog has it's own set of potential issues so you may be trading hip dysplasia for something else. Even if it's a mutt. Even if you had perfect nutrition. Even if you exercised the dog perfectly.
In fact, there are no guarantees when it comes to animals in general...........and that's what makes them wonderful :)