Hip
Dysplasia is ~40% inherited and is controlled by the
genetic make-up (genotype) of the individual dog. The genotype is determined
by the genes received from the parents - one half from the sire and one half
from the dam. The current concept is that hip dysplasia is a polygenic trait
meaning that many genes affect that trait. It is also been found to be related
to growth rates. Over feeding your puppy can make it grow too quick putting
extra pressure on the dogs joints and so increasing the risks of hip dysplasia.
The hip joint is the part of the skeletal system that joins the structures of
the rear limb with the pelvis. It is the focal point for transfer of driving
power, generated by the rear limbs, to the remainder of the body.
The
hip is a ball and socket joint. Normal function depends on a good fit of the
ball (head of the femur) within the socket (acetabulem) The surfaces of the
head of the femur and acetabulem are covered with smooth articular cartilage.
The joint is encased by a specialized type of connective tissue called the
joint capsule and this produces a joint fluid which lubricates and nourishes
the articular cartilage.
Normal development of the hip, from birth to maturity, is determined by how
well the parts fit together. Dogs of all ages are subject to the
symptoms of hip dysplasia and the resultant osteoarthritis. In severe cases,
puppies as young as five months will begin to show pain and discomfort during
and after vigorous exercise. The condition will worsen until even normal daily
activities are painful. Without intervention, these dogs may be unable to walk
at all by a couple years of age. In most cases, however, the symptoms do not
begin to show until the middle or later years in the dog's life.
Nutrition may be another risk factor. One of them is through obesity. It stands to reason that carrying around extra weight will exacerbate degeneration of the joint in a dog with a loose hip. Overweight dogs are therefore at a much higher risk. Another factor that may increase the incidence is rapid growth in a puppy during the ages from three to ten months. Experimentally, the incidence has been increased in genetically susceptible dogs when they are given free choice high protein, calcium and high calorie diets.
Exercise may be another risk factor. It appears that dogs that are genetically susceptible to the disease may have an increased incidence of disease if they over-exercised at a young age. But at the same time, we know that dogs with large and prominent leg muscle mass are less likely to contract the disease than dogs with small muscle mass. So exercising and maintaining good muscle mass may actually decrease the incidence of the disease. Moderate exercise that strengthens the gluteal muscles, such as running and swimming, is probably a good idea. Whereas, activities that apply a lot of force to the joint are contraindicated. An example would be jumping activities such as playing Frisbee.