15 week old choc lab with large joints

Question
We have a 15 week old choc lab and the vet is concerned over the size of his joints.  It is espically noticable in the front legs.  His elbows kind of point out and look large almost like a bull dog would stand.  Do you think this is genetics or something else.  HIs mother was yellow and father black, both akc registred with papers as is our puppy.  both parents have been checked and certifed for hips.

Answer
What has he been eating and how much of it?  Diet is absolutely critical to large breed puppies.  The worst thing you can do is feed one too much of too rich of a diet.  The problem could have been caused by too much calcium and in the wrong ratio to phosphorus.  What I would do is put him on a common brand of dry ADULT chow and nothing else, and not too much of it.  The various service dog schools are highly successful making an early switch to adult chow and feeding nothing else, and NO supplements.  

Is your vet familiar with the work of Kealy in Kealy, et al. "Effects of limited food consumption on the incidence of hip dysplasia in growing dogs." JAVMA, v201, n6 Sept. 15 1992.

How is his weight?  Your dog definitely should be narrower at the waist than the hips and chest. You should be able to easily feel the ribs, but not see them.  Each dog is different.  Standard recommendations are a good place to start, but each dog must have its food and exercise adjusted to its individual needs. Here is a link to a good illustrated guide, http://www.longliveyourdog.com/twoplus/RateYourDog.aspx