Genetic or Environmental
M.C. Wakeman, D.V.M.
One frequently encounters discussions which assert that hip dysplasia is 50% genetics
and 50% environment. We prefer to think of it as 100% genetics, then 100% environment.
Genetic considerations are the entirety of what we must as breeders consider. Once that
puppy is born, environment is 100% of how well that puppy will do within the possibility of
his genetics. Dogs with very good hips, congenitally, may have an injury and end up
diagnosed as having 'unilateral hip dysplasia'. Individuals with very shallow sockets may
be mobile and free of pain to an advanced age, if they have unlimited exercise. This is the
entirety of what the owner of that puppy needs to concern himself with to provide the best
possible care for his dog.
Over the years, our observations of the kennel populations of giant breeds and their
siblings living in private homes have led to the conclusion that there is no such thing as
congenital unilateral hip dysplasia, but only acquired unilateral hip dysplasia. The kennel
dogs, whose exercise opportunities are maximized, with several dogs of a similar age free
to run and play all day and night in large paddocks, show us some interesting things.
They grow much more slowly, because much of their food intake goes into play and
They rarely (almost never) suffer an injury.
They always have symmetrical hip sockets, even if they are very shallow.
Their litter mates in private homes, where exercise is confined to an hour or two of intense
play or jogging when their owners return from work, provide us with a different set of
They grow very large, very fast.
They often suffer injury.
They frequently have hip sockets of different depths.
The implications of these observations are enormous, but very simple to understand.
These large breeds grow much too quickly for their biology to keep up. They frequently
show some degree of clinical rickets with some bowing of the forelegs, and have large soft
joints due to the inability of the body to deposit calcium in the bone at a rate equal to the
rate of growth. They often show uneven growth, with the rear end growing over a few
weeks, then the front end trying to catch up. As the rear leg assembly grows
disproportionately, and the puppy is 'high in the rear', the mechanical leverage that the
muscles are able to exert across these straighter angles is much reduced. The result of
this is a decreased ability of muscle to protect joints from injury.
The owners of giant breed pets tend to overfeed their puppies, having with the best of
intention, the inner desire to see a 'big dog' and to do nothing which might risk the dog not
attaining the greatest possible size. Try as they may, some owners are just unable to
restrict their puppy's diet. Owners are cautioned that their puppy needs a good deal of
exercise, but their work schedules often conflict with their desire to do this. The result is a
period of intense exercise. A 3 mile run, or a half hour of Frisbee. When a single puppy who
lies around all day welcomes his owners in the evening, he is ill prepared for either intense
exercise, or the uncertainty of footing on slippery floors and his always changing joint
angulation. His muscle tone is a small fraction of that of a puppy which plays with other
active dogs all day long. The result is an injury.
When any dog has a hip dislocated, if it is not repaired within 48 hours, the socket begins
to lose depth. When an injury occurs to a rear leg, whether it be a toe injury, a stifle injury,
a soft tissue injury, or a hip injury, the result is often a decreased amount of weight bearing
on that leg over a period of days to weeks or months. When this happens, the mechanical
forces applied to the living bone tissue change, and the hips become asymmetrical, the
injured hip becoming shallower in a similar fashion.
Many will find that a very controversial statement. Dr. Corley from the OFA would reply to
observations such as this, that he could prove that unilateral hip dysplasia was genetic,
since it was almost always the left hip which was shallower. My response to his statement
was that this proves to me that most dogs are right handed. The left diagonal being the
master limb, the one with which the dog pushes off most strongly, and the one which is
most liable to injury, especially stifle injury.
The conclusion from these observations is that the single most important environmental
factor in a puppy's life is exercise, continuous and strenuous. Since this is often
impossible for owners to arrange, the next considerations are to drastically restrict the diet
of the growing puppy and to avoid strenuous exercise which will exhaust his muscles and
leave him unable to protect his joints from injury. The puppy should be given frequent
moderate exercise instead. This requires a different kind of time commitment from the