Hypothesis One: Joint Malformation

In this case, the femoral head may not fit into the acetabulum properly due to 
faulty development. The cause is usually a complex mix of genetics and environment Ð 
large breed dogs, especially Rottweilers, are often predisposed to congenital shallowness 
of the acetabulum and/or insufficient size of the femoral head.  This results in joint laxity 
and subsequent subluxation or luxation of femoral head from the acetabulum.  Instead of 
rotating in the acetabulum, the femoral head tends to slide back and forth causing 
abrasion and irregular wear.
Abrasion between the femoral head and acetabulum causes the articular cartilage 
to undergo degeneration.  This resultant secondary degeneration of the joint then leads to 
thickened cancellous trebeculae and osteophyte development.  Despite the bodyÕs 
attempts to stabilize the joint, degenerative changes continue. These degenerative 
changes cause massive inflammation within the joint, resulting in pain via inflammatory 
mediators.
Many of JocelynÕs  clinical signs correlate with this condition, such as 
disproportionate amount of weight being carried in forelegs, hip joint pain during 
palpation that was more obvious during extension than flexion, reduced hip range of 
motion, and a positive Ortalani sign.