Diagnosis

Our initial three hypotheses in this case were trauma, nutritional inadequacies, and 
developmental joint disorder, all of the hip. We isolated the problem to the hip area early 
on in the case based on the facts given by the owner and findings on the initial physical 
exam ( all other joints appeared stable and nonpainful). After the animal was sedated, 
another orthopedic exam was performed which confirmed that the problem was in the hip 
joint ( positive Ortalani in both hips, and increase ROM and confirmed joint stability in 
the stifles). Radiographs also confirmed abnormalities in the hip joint. The acetabulum 
was shallow and there were changes visible on the femoral head, as well as subluxation 
of both femoral heads. Based on these findings, the breed, size and age of the animal we 
have diagnosed Jocelyn with bilateral hip dysplasia.

 Hip dysplasia is an abnormal development of the hip joint usually bilaterally. The 
disease process is multifactorial. Dysplastic dogs are born with normal hip joints and 
subsequently undergo progressive structural changes. The disease is actually preventable 
if hip joint congruity is maintained starting at an early age. This would allow the 
acetabulum time to ossify and allow the surrounding soft tissue to become strong enough 
to prevent femoral head subluxation. Unfortunately, most cases are not prevented. The 
main factors contributing to hip dysplasia are a combination of congenital predisposition 
for the disease, breed and nutrition. The congenital predisposition to dislocation of the 
hip involves many genes. The genes do not actually affect the skeleton, but, rather, the 
cartilage, the supporting connective tissue, and muscles of the hip region. Biochemically, 
the disease represents a difference in the growth of the muscle mass and the 
disproportionate growth of the skeleton. This, in and of itself, is inherent to large breed 
dogs. This particular problem can further be enhanced by improper nutrition. Increased 
caloric intake and over supplementation of nutrients and minerals, especially calcium add 
to the rapid growth of muscle mass in relation to the skeletal growth and rapid 
ossification of the bones/cartilage.   The combination of these pathophysiologic processes 
leads to joint laxity ( caused by failure of muscles to develop and reach functional 
maturity concurrently with the skeleton). Most of the other changes are subsequent to the 
joint laxity. These include swelling, fraying, and rupture of the teres ligament, shallow 
articular cavities, and subluxation of the femoral head. As subluxation occurs there is a 
decrease in the weight bearing contact area of the femoral head and acetabulum. This 
concentrates the force over a smaller area, leading to more rapid erosion of the articular 
cartilage.  Loss of the articular cartilage leads to a large part of the pain because it 
exposes the subchondral bone to wear. The subchondral bone contains the nocireceptors 
which, when stimulated by the constant friction, leads to the pain. In addition, there is  
eburnation of subchondral bone ( harding into ivory like mass, which is more susceptible 
to constant remodelling. If the articular cartilage was intact and stable the femoral head 
would be more protected), remodelling of the acetabular rim, and femoral head, and 
periarticular osteophyte formation. As the loss of articular cartilage continues , there is 
thickening of the joint capsule in an attempt to stabilize the joint. The osteophytes form 
along the attachment of the joint capsule to the femoral head and acetabular rim 
Osteophyte formation also contributes to the pain.  Eventhough the joint capsule 
thickening may stablilize the joint, degenerative changes will continue due to the 
abnormal joint surfaces unless there is intervention.

Jocelyn, being a large breed dog (Rottweiller ) was already predisposed to hip dysplasia. 
The fact that she was feed free choice large breed Iams dog food may have contributed to 
the disease process as outlined above. Once again, based on our current knowledge of hip 
dysplasia and the nutritional and inherent factors revolving JocelynŐs particular case, we 
diagnose her with Hip Dysplasia.