HIP Dysplasia is the most common cause of rear leg lameness in dogs.
The highest incidence occurs in large-breed dogs, including St. Bernards,
Newfoundlands, Rottweilers, Chesapeake Bay Retrievers, Golden Retrievers,
German Shepherd Dogs, Labrador Retrievers, and many others. Smaller breeds are
also affected, but are less likely to show symptoms.
Hip dysplasia is a polygenic trait. That is, more than one gene
controls the inheritance. Environmental factors such as diet are also involved.
The hip is a ball-and-socket joint; the ball is the head of the femur and the
socket is the acetabulum of the pelvis. In a dysplastic hip, the head of the
femur fits loosely into a poorly developed, shallow acetabulum. Joint
instability occurs as muscle development lags behind the rate of skeletal
growth. As the stress of weight-bearing exceeds the strength limits of the
supporting connective tissue and muscle, the joint becomes loose and unstable.
This allows for free play of the femoral head in the acetabulum, which promotes
abnormal wear and tear.
Feeding a very high-calorie diet to growing dogs can exacerbate a
predisposition to hip dysplasia, because the rapid weight gain places increased
stress on the hips. Being overweight supports the genetic potential for hip
dysplasia, as well as other skeletal diseases. A diet with an imbalance of calcium
and phosphorous is bad for bone development.
Another factor that can bring on the symptoms of hip dysplasia is
inappropriate exercise during the period of rapid bone growth. Young dogs
should be discouraged from jumping up and down from heights in situations where
they land on their back legs (such as jumping up to catch a ball), and from
standing up on their back legs (which dogs do when they stand up against a
fence or window to get a better view). They should also avoid running on
pavement.
Dogs with hip dysplasia are born with hips that appear normal but
progressively undergo structural changes. The age of onset is 4 to 12 months.
Affected puppies may show pain in the hip, walk with a limp or a swaying gait,
bunny hop when running, and experience difficulty in the hindquarters when
getting up. Pressing on the rump can cause the pelvis to drop. With the puppy
on his back, the rear legs may not extend into the frog-leg position without
causing pain.
An X-ray of the hips and pelvis is the only reliable way of
determining whether a dog has hip dysplasia. Good X-rays require heavy sedation
or anaesthesia. The standard view is taken with the dog lying on his back with
his rear legs parallel and extended. The knees (stifles) are rotated
internally. Care is taken to be sure the pelvis is not tilted.
Here at Working Gundogs we have all our Labrador Retriever breeding stock tested for Hip Dysplasia, the results can be found on the Kennel Club website under Health Checker.
