Jocelyn is a large-breed (Rottweiler) puppy on free choice puppy food, which allows for excessively rapid growth.  In many large and giant breed dogs with a certain genetically predisposed vulnerability rapid growth, combined with several other environmental factors often leads to developmental abnormalities.  Jocelyn weighs 73 lbs., which is large for a 9-month-old puppy. Through such an exponential increase in size and mass, increased pressure and strain are placed on the dog's joints. The surrounding muscles are not yet strong enough to keep up with her size and weight.  Therefore, the ball and socket joint becomes loosened.  This increased and abnormal movement often results in the subluxation of the femoral head, as evidenced by the positive Ortalani sign.    This will change the compression, stress, traction and congruity between the femoral head and acetabulum.  The abnormal mechanical forces of traction and compression cause the round ligament and the liganentum teres to become stretched and swollen. The position of femoral head on the acetabulum results in a decreased surface area to absorb the shock and compression associated with this joint.   The continual rubbing of the dorsal surface of the femoral head against the rim the acetabulum results in erosion of the articular cartilage.  This degenerative process continues and is self-perpetuating.  Cartilage erosion exposes the subchondral nerve endings and accounts for the pain.  We expect to see radiographic changes illuminating the bony changes found in malformation of the hip joint.  We would expect to see flattening of the femoral head, and a shallow acetabulum.  Additionally, osteophytes at the insertion of the joint capsule on the femoral neck would be expected.