WHAT IS IT: "Hip
dysplasia" simply stated means an "abnormal formation" of the hip joint.
Think of the condition first as a looseness in a joint that should be
snug - then most of the problems attendant to hip dysplasia are a result
of this "looseness". See the image on the right a few paragraphs down
for an example of a nice, normal, snug hip joint.
The normal anatomy of the hip joint is a classic Ball and Socket joint.
The head of the femur (the "Ball") is supposed to match the acetabulum
(the "Socket"). A good hip joint has a neat, snug fit between the ball
and socket - that is, the head of the femur should not be slipping and
slopping around somewhere in the neighborhood of the acetabulum!
There are infinite variations of dysplasia - ranging from only very
slight changes from normal to complete dislocation. (There are a number
of examples of actual radiographs in the table near the bottom of this
page. Click on any x-ray image to enlarge it.) Consequently, no two
dogs will be affected by CHD exactly alike.
HOW IS CHD ACQUIRED? This is one disorder that has been proven,
positively, to have a genetic basis. How much of a genetic origin in
each case can vary from 25% to 85%. A condition that is completely
determined by genetics, for example gender, has a Heritibility Factor of
1. A condition totally unaffected by genetics, for example a broken
leg, has a Heritibility Factor of zero.
Studies have shown that CHD's Heritibility factor ranges from .25 to
.85; this is a significant genetic contribution. So the Heritibility
Factor for a given dog is the result of a combination of the
Heritibility Factors from each parent. Simply put . . . if the parents
are carrying genetic material for hip dysplasia - so will the
offspring. And the greater the genetic contribution for loose hips or
malformed bone or abnormal muscle mass (Heritibility Factor) from
the parents, the greater the chances for hip dysplasia in the offspring.
The expression of hip dysplasia in any dog has other determinants,
though; genetics play only a varying role in the total picture. The
effect of the developing dog's environment does play a role in the
clinical (observable) signs of dysplasia, although just like the genetic
component the effects of environment are variable and not completely
understood. To illustrate the complexity of the environmental issue,
listen to this: It is possible for a dog with known genetic components
for hip dysplasia (called genotype) to not show any clinical signs of
trouble if the environmental factors are favorable. So the dog can be
dysplastic and not show observable signs of it until middle or old age.
I have seen this fairly commonly in practice and it is always an
important issue with breeders who assume that their dog is normal just
because it hasn't shown any signs of hip trouble. Why take pelvic
x-rays for dysplasia when the dog has always acted perfectly fit, they
reason. There is no excuse for NOT taking pre-breeding x-rays. I
have seen a number of breeders who sold litters of pups where the
parents have not been x-rayed for CHD and who were shocked a year or so
later when the phone started ringing about "that pup you sold has hip
dysplasia". Trust me, it happens. Also, if two dogs that have the
same genotype (genetic makeup) are exposed to different environmental
conditions, their expression of hip trouble can be quite dissimilar.
Little wonder that the topic has such a wide range of information and
misinformation regarding it.
Some of the environmental aspects that can affect the observable
expression of hip dysplasia are the following:
1. Nutrition - There are reports that in puppies a restricted
calorie intake could restricted the growth rate, and in turn will lessen
the potential for the dog to develop hip dysplasia. (I wouldn't suggest
doing this to any pup... it makes as much sense as stealing money from
your own checking account!) The problem is that some restricted diets
restrict the fat and protein content and increase the carbohydrate
content of the food. Bad! See a better way in the discussion in
The real goal should be to keep growing pups from becoming OVERWEIGHT.
Restricting fat and protein in a growing pup can be a disaster. A high
quality, meat-based diet is absolutely necessary for growing pups, just
don't feed so much of it that the pup becomes overweight.
Physical Activity - In a young, growing dog with a genotype
(genetic makeup) for CHD who will eventually develop some trouble
because of it, and will develop more arthritis and have more eventual
difficulty if it is highly active physically. Climbing stairs, jumping
into and out of pick-up trucks, running with other normal dogs can all
subject the growing hip structures to unwarranted stress and trauma and
increase future discomfort for the dog. The effects of this excessive
activity is worsened in an overweight pup. (In a normal, growing dog,
all these activities will not cause hip dysplasia!)
3. Bedding - There is no scientific proof,
but lots of
observational conclusions, that pups reared especially during the
nursing period on slippery surfaces such as newspapers will be prone to
hip difficulties. That is not to say that smooth concrete, wood or
newspaper surfaces cause dysplasia, just that they can make a bad
situation worse. Better surfaces for newborn pups would be blankets or
towels... something they can get a better grip on.
MUSCLE AND CHD: Research has shown that dogs with CHD have
significantly decreased sizes of total pelvic musculature surrounding
and acting on the hip joint. Whether this is a contributing factor or a
result of hip dysplasia remains to be proven.
One muscle that can contribute to worsening of hip dysplasia is the
Pectineus Muscle. In dogs with a strong genetic background for CHD,
the microscopic makeup and contractibility of the Pectineus Muscle are
strikingly different from the same muscle of normal dogs. The theory is
that a tight or inelastic Pectineus Muscle causes tension in such a
direction that the force tends to pull the head of the femur away from
the acetabulum. So the tight muscle creates more looseness in the
joint. I have had good results in about 50% of the cases I have
surgically excised a portion of the Pectineus Muscle. The patients were
more comfortable and mobile almost immediately. This Pectineal Myotomy
surgery has no effect on the arthritic changes in the hip joints; it can
make the dog more comfortable.
LIGAMENT OF THE HEAD OF THE FEMUR: Attaching to the head of the
femur from the center of the hip socket is a tough fibrous ligament
called the Ligament of the Head of the Femur. If this ligament is
stretched or torn, the hip joint will be less stable . . . and this is
exactly what happens to dogs with dysplasia. In fact, some of the first
changes to take place in young dogs developing hip dysplasia occur in
this ligament especially if the muscle mass of the pelvis is
underdeveloped. The ligament swells, develops tiny tears and
stretches. In advanced CHD this ligament can totally break down and
cause more harm than good.
JOINT CAPSULE: This tissue, which if you could hold it, would
feel like the wall of a thick balloon It surrounds the joint and
produces synovial fluid to nourish and lubricate the joint cartilage.
In addition, the joint capsule provides some support to the joint.
In dysplastic joints the capsule becomes irritated, stretched, and
scarred. In advanced cases the capsule will lose its elasticity and
inhibit a full range of motion in the joint. A large percentage of the
pain associated with hip dysplasia originates from inflamed nerve
endings in the joint capsule so any pathology here will have a
noticeable affect on the dog.
CARTILAGE: The surfaces of the head of the femur and the
acetabulum are covered with what is termed hyaline cartilage. In a
dysplastic joint the points of pressure and the amount of pressure
applied to areas of cartilage surfaces are abnormal. The cartilage is
being asked to do things it physically cannot accomplish, so it changes
or disintegrates as a response. The changes range from thickening in
abnormal areas to thinning in others. Sometimes the pounding it gets
erodes the cartilage down to the underlying bone! The outcome is more
pain and discomfort, more inflammation, more calcium deposits from
inadequate healing attempts and eventual breakdown of the joint as a
unit. Nutriceuticals such as Chondroitin Sulfate and Glucosamine may be
effective in aiding the repair and maintenance of this articular
BONE CHANGES: Since bone is alive it responds to stress and grows
in a manner that tends to distribute weight loads evenly. As a result
of posture changes brought on by discomfort, the dog's weight bearing
forces stress the bone in
The bone does what it is supposed to do as a response and changes its
shape. The bone doesn't know that the shape it changes to
Ultimately, this abnormal shape to the thigh bone and acetabulum create
more difficulty with stability and a vicious cycle ensues that spells
trouble for the dog. See the images below for a comparison of
before/after bony changes. The final outcome of bony remodeling in
unstable hip joints is Degenerative Joint Disease.
SIGNS OF CHD IN YOUNG DOGS: What you will see first is a pup that
runs with both back legs nearly together, almost like a rabbit would
run. After exercise the pup will be reluctant to rise, will sit back as
if unsteady and will have difficulty climbing stairs or inclines. The
pup might look slightly underdeveloped in the rear quarters. When it
stands the rear legs may not be parallel, but rather too near each other
at the hocks (ankles) called "cow hocked".
You might notice a boniness to the pelvic area from lack of good muscle
development. Another hint of trouble is an inability to extend the leg
backward very far (decreased range of motion). Note: Many pups rest or
sleep in a frog-like position with knees extended out to either side -
this is a good sign and shouldn't alarm you.
In severe cases of dysplasia, the young dog will rock forward to support
more weight on the front legs (which can create trouble in the shoulders
and elbows). When dogs do this it seems as if they are tip-toeing or
walking very lightly on their rear legs. A dysplastic pup will be
reluctant to jump or "stand up" on its hind legs. Signs usually being
between five and eights months of age. But remember, as we learned
above, some dogs do not show any signs at all of hip joint degeneration
until mature adults.
AN INTERESTING CASE:
Here is a classic example of why it is so important to take a radiograph
of the sire and bitch prior to
In this example the owner had a two year old male Golden Retriever that
was totally healthy by any observable standards. It ran, jumped, swam
and had never showed any kind of lameness. The owner had the dog
x-rayed and guess what? The film displayed severe abnormalities in the
left hip joint. Were the changes due to a genetic propensity for hip
joint abnormalities? Or was this actually due to an injury early in the
pup's life that impacted the proper growth of the joint structures? No
one can say for certain. But IF the abnormal hip was due to genetic
determiners why take a chance that, if bred, the litter might have even
worse hip joint conformation? The owner decided not to breed the dog.
SIGNS OF CHD IN OLDER DOGS: Some dogs with dysplasia escape pain
or simply accept it as a fact of life and don't complain until
degenerative joint disease sets in. Affected dogs will sit rather than
stand, have trouble arising, run with the rear legs together and not be
able to keep up any more on Sunday walks. Every veterinarian has been
mystified on occasions where an x-ray of an older dog, who only recently
seemed to be having hip trouble, reveals extensive degenerative changes
in the hips due to long term dysplasia.
It is very important to keep this fact in mind: A dog can appear normal
and yet have hip dysplasia. Just because a four-year-old dog isn't
showing signs of trouble is not sufficient evidence to state "it
couldn't possibly have hip dysplasia". I have heard supposedly
responsible breeders make that statement and it takes lots of convincing
to get them to believe otherwise.
If you are involved with a breed in which CHD has been reported, and you
wish to improve the breed as well as have happy owners of your pups you
must know if your breeding stock is prone to CHD. And neither you, your
cousin, the mailman OR your veterinarian can tell if your dog has CHD
unless some basic guidelines are followed.
DETERMINING THE PRESENCE OF CHD: Dogs with obvious signs of CHD
(hip soreness, difficulty arising or climbing inclines, muscle atrophy
over the rump, limping) are not a challenge to confirm as such. So this
discussion will apply more to the dog that seems to be normal but
you are either not sure or need to know for breeding or training/working
reasons. The minimum data required is a pelvic x-ray taken under
anesthesia . . . PERIOD! You MUST have the x-ray to know if the dog is
(University of Pennsylvania
See an entire article about PennHIP
Commercially available since 1993, this procedure has been and was
developed as an objective method of evaluating dogs’ hip
structure. It evolved as a direct result of the subjectivity factors
and age constraint (maturity) limitations inherent to evaluation and
certification of dogs by the OFA and other screening programs. PennHIP
research published in peer reviewed journals has shown that different
breeds have different susceptibility to osteoarthritis. Therefore, in
PennHIP evaluations each breed is compared to its own. Only PennHIP
certified veterinarians can do the PennHIP evaluation but many
veterinarians are becoming certified in this procedure.
Why is anesthesia required
in order to have the dog radiographed? To have an x-ray that yields the
information you're trying to discover the dog must be perfectly
relaxed. Because the position required to take a diagnostic x-ray is a
somewhat unnatural one, even very gentle,
cooperative dogs cannot relax enough to be x-rayed properly. See the
x-ray on the right. It is a great example of poor positioning.
(Click on it to enlarge.) The dog is tilted to its left (to our right)
and the view we see of the structures is imbalanced. One hip looks OK
and the other bad but in reality this view is worthless. Nothing is more
frustrating for the veterinarian than to have an owner say "I need to
know if this dog has any signs of hip dysplasia. Take an x-ray, but I
don't want you to use anesthesia; this dog will do anything you tell it
to do, so an anesthetic isn't necessary." Unless at the time of
exposure of the x-ray, the dog is positioned precisely, with no
movement, the x-ray will not be credible. You won't get the information
you need! Your veterinarian will look for an x-ray image that looks
like the nice, normal hip at the beginning of this article.
Another great advantage of
anesthesia is that the veterinarian can only then palpate and manipulate
the hips to actually feel the degree of looseness. Also, the tension of
the Pectineus Muscle is best assessed under anesthesia. Any grating or
grinding from calcium deposits along the hip joints can be evaluated
better than attempting to do so on an awake patient. If you need the
information, the dog needs the anesthetic.
If the pelvis is tipped only slightly to one side or the other, one hip
can appear normal that isn't and one can appear dysplastic that isn't!
To complicate things, 10% of dysplastic dogs will be affected in only
one hip! Better do the x-ray right!
The importance of radiography cannot be overstated. It can be done
early, say five or six months of age, if dysplasia is suspected. If the
results are questionable, reserve breeding until a time when the x-rays
are conclusive. Generally, by the time the dog is full grown the x-rays
will properly reveal the status of the hips. The OFA (OFA.org) will not
classify hips in dogs until they are two years of age.
The advantage of radiography in a younger animal is that if you plan on
breeding it you can eliminate fruitless time and financial and emotional
expense related to breeding if the x-rays show unquestionable hip
dysplasia. There have been many disappointed, depressed dog owners
whose expectations for breeding were high and were shocked back to
reality when their two-year-old dog showed x-ray evidence of dysplasia...
two years of planning, training and dreams of great litters down the
tube. If only the parents had been x-rayed. If only preliminary x-ray
were taken eighteen months ago. Again, the advantage of the PennHIP
procedure is obvious since dogs over 4 months of age can be evaluated.
It is very sad indeed for
any pet owner to see their special pal affected by the discomfort and
mobility problems associated with Canine Hip Dysplasia. Fortunately,
armed with knowledge and forethought, highly selective breeding is your
best defense against CHD.
inspection you can click on any of the images below to see
a full sized photo in a new window.