Hip dysplasia is a condition that frightens many owners although in truth most dogs can live a normal, productive and otherwise healthy life - even with quite severe hip disease present.  There is evidence to show that the severity of the changes in the hips (as seen on an x-ray) is NOT directly related to the amount of pain shown by an animal.  Nevertheless, hip dysplasia can be a debilitating disease and there is a strong hereditary influence - so responsible breeders should have their animals screened by their veterinarian and scored by the BVA/KC Scheme and avoid breeding from the worst affected individuals.

If HD was caused by a single factor then it would have been fully understood and largely overcome by now. It is known that two factors determine whether HD is to occur and if so, how bad it will be - inheritance and what is termed 'environment'.  The former relates to the genetic code passed to the offspring by both parents and the latter to all the outside influences which alter and mould the growth and functions of the bones, cartilage, ligaments, tendons and muscles of the body. It is argued that dogs are not born with hips affected by dysplasia (unlike humans).  Hip modelling, otherwise termed development can worsen with the passing of time, most particularly during the rapid growth phase between 14 and 26 weeks of age. 

In simplistic terms the genetic code is rather like the architect's building blue prints and, the environment, the builders and their materials.  In HD the architect gets things wrong to a greater or lesser extent but the builders have the greater influence on how things look and function in the final analysis.

To understand hip dysplasia we must have a basic understanding of the joint that is being affected.  The hip joint forms the attachment of the hind leg to the body and is a ball and socket joint.  The ball portion is the head of the femur while the socket (acetabulum) is located on the pelvis.  In a normal joint the ball rotates freely within the socket.  To facilitate movement the bones are shaped to perfectly match each other; with the socket surrounding the ball.  To strengthen the joint, the two bones are held together by a strong ligament.  The ligament attaches the femoral head directly to the acetabulum.  Also, the joint capsule, which is a very strong band of connective tissue, encircles the two bones adding further stability.  The area where the bones actually touch each other is called the articular surface.  It is perfectly smooth and cushioned with a layer of spongy cartilage.  In addition, the joint contains a highly viscous fluid that lubricates the articular surfaces.  In a dog with normal hips, all of these factors work together to cause the joint to function smoothly and with stability.

Normal Hips

Hip Dysplasia

Hip dysplasia is caused by a laxity of the muscles, connective tissue and ligaments that would normally support the joint.  As this happens, the articular surfaces of the two bones lose contact with each other.  This separation of the two bones within the joint is called a SUBLUXATION and this causes a drastic change in the size and shape of the articular surfaces.  Most dysplastic dogs are born with normal hips but due to their genetic make up and possibly other factors, the soft tissues that surround the joint develop abnormally causing the subluxation.  It is this subluxation and the remodelling of the hip that lead to the symptoms we associate with this disease.

HIP SCORING

Any GSD which is to be considered for breeding must have an x-ray taken of its hips after its first birthday and submit the x-ray plates to the BVA/KC Hip Dysplasia Scheme where they are assessed by means of scoring.  The hip score is the sum of the points awarded for each of nine radiographic features of both hip joints.  THE LOWER THE SCORE THE LESS THE DEGREE OF HIP DYSPLASIA PRESENT.  The minimum (best) score for each hip is zero and the maximum (worst) is 53, giving a range for the total of 0 to 106.
The average score of the breed (breed mean score) is calculated from all the recorded scores for a given breed.  The Breed Mean Score for German Shepherds is currently 19

Whilst we accept that the causes of hip dysplasia are considered heritable, new research conclusively suggests that environment also plays a role.  To what degree is genetic and what portion environmental is a topic of current debate.  Environmental  influences would include overweight, injury at a young age, overexertion on hip joint at a young age, ligament tear at a young age, repetitive motion on forming joint (ie jogging with a puppy under 1 year of age).  As current studies progress, greater information will help provide procedures to effectively reduce the occurrence of this condition, however, what we do currently know about diet and exercise are listed:

NUTRITION: It appears that the amount of calories a dog consumes and when in the dog's life those calories are consumed have the biggest impact on whether or not a dog genetically prone to hip dysplasia will develop the disease.

Experimentally, it has been shown that obesity can increase the severity of the disease in genetically susceptible animals.  It stands to reason that carrying around extra weight will exacerbate the degeneration of the joints in a dog; including the hip.  Dogs that may have been born genetically prone to hip dysplasia and are overweight are therefore at a much higher risk of developing hip dysplasia.

Another factor that may increase the incidence of hip dysplasia is rapid growth in puppies during the ages from three to ten months.  Experimentally, the incidence has been increased in genetically susceptible dogs when they are given free choice food.  In one study, Labrador Retriever puppies fed free choice for three years had a much higher incidence of hip dysplasia than their littermates who were fed the same diet but in an amount that was 25% less than that fed to the free-choice group.

Feeding a diet that has too much or too little calcium or other minerals can also have a detrimental effect on the development of the hip joint.  However, with today's complete and balanced dog foods this has become a rare occurrence.  The practice of feeding home-made dog foods is popular with some dog owners.  These diets must be carefully monitored for proper nutritional balance; not only for calcium and the other essential minerals but for all nutrients.

EXERCISE: 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-exercise at a young age.  But at the same time, we know that dogs with large and prominent let 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.