The thought of hip dysplasia is enough to strike fear into any large breed dog lover. For that reason, the bulk of research on spay / neuter and joint disease is focused on this disorder.
Dogs who are sterilized before the age of six months have a 70% increased risk of developing hip dysplasia. The authors of this study (Spain et al, JAVMA 2004), propose that “it is possible that the increase in bone length that results from early-age gonadectomy results in changes in joint conformation, which could lead to a diagnosis of hip dysplasia.”
There is more evidence that spay / neuter can increase the risk of hip dysplasia. Van Hagen et al (Am J Vet Res, Feb 2005), found that of the sample dogs diagnosed with hip dysplasia, those that were neutered six months prior to the diagnosis were nearly twice as likely to develop hip dysplasia.
Interestingly, a study by Dannuccia et al (Calcif Tissue Int, 1986), found that removing the ovaries of Beagles caused increased remodeling of the pelvic bone, which also suggests an increased risk of hip dysplasia with sterilization