This article is from the Canine Medical Information FAQ, by Cindy Tittle Moore with numerous contributions by others.
There is no known method of preventing hip dysplasia except for a
thoughtful and carefully executed breeding program with regular
radiographic analysis of all stock before breeding. It is possible to
reduce symptoms entirely to the point where the dog will radiograph
much less severely , however followup studies show that these dog's
offspring have the same risk for HD as they would have whether the
parents had been so treated . The implication is that it is
unethical to use as breeding stock dogs that were treated to prevent
their symptoms from disappearing. On the other hand, pet owners with
no intention of breeding their dogs might consider reading .
 Kealy, et al. "Effects of limited food consumption on the
incidence of hip dysplasia in growing dogs." JAVMA, v201, n6 Sept 15
 Willis, Malcom, _Genetics of the Dog_.
_Radiographic Diagnosis and Control of Canine Hip Dysplasia_ by Joe P.
Morgan, DVM, Vet.med.dr. (Stockholm) and Michele Stephens, DVM.