Hip Joint Malformation

Why?  Clinical signs
1. Both hips seem lame, right hind worse
2. Uncomfortable sitting- increased weight on rear legs
3. Disproportional amount of weight carried on front legs
4. Pain on movement in orthopedic exam
5. Ortalani sign

Etiologies of possible malformations:
1. Previous undiagnosed trauma leading to irregular healing of bones, damage to 
ligaments, damage to synovial cartilage, avascular necrosis of femoral head
2. Osteomalacia/fibrous osteodystrophy.  Mineral imbalances leading to bone 
demineralization, remodeling with fibrosis, bone deformity, physical disruption 
of joint.
3. Hypertrophic osteodystrophy/osteochondrosis.  Pathologic process at epiphysis 
compromising bone structure
4. Neoplasia.  Neoplastic proliferation compromising joint conformation.
5. Genetic.  Heritable developmental abnormality of hip joint.  Hip dysplasia: 
shallow acetabulum, flattened femoral head


Consequences of malformation:
1. Increase joint laxity and instability allowing ortalani sign.
2. Abnormal forces as consequence of movement-concentration of weight bearing 
forces and subsequent subluxation.
3. Accelerated wear and degeneration of articular cartilage- degenerative joint 
disease.  Erosion of cartilage, possible joint mice rough articular surfaces, 
increased friction, exposure of subchondral bone, pressure on nerves leading to 
pain.  Osteoarthritis.
4. Thickening of joint capsule.
5. Changing sites of attachment of joint capsule.
6. Remodeling of femoral head and neck
7. Osteophyte development.  Bone remodeling in articular space. 



Compromising factors in JocelynŐs case:
1. Size and weight.  Large breed dogs prone to more developmental conditions.  
Obesity exacerbates joint problems.
2. Level of activity.  With increased activity see increased friction and 
subsequent erosion.
3. Nutrition.  Feeding large breeds for maximal growth rate (free choice) causes 
body weight to increase before skeleton is ready to handle that amount of 
stress.  Any previous genetic abnormalities will be accentuated by increased 
stress on the joints.


The above mentioned factors would combine to exacerbate any genetically 
preexisting factors.  The most likely cause in this case would be hip dysplasia 
though other developmental abnormalities cannot be completely ruled out without 
radiographs.  The movement of the femoral head in the acetabulum would cause 
joint erosion (see hypothesis1 for further info).

  
Diagnostic plan:
1. More thorough orthopedic examination under anesthesia.  Evaluate ortalani 
sign and any other abnormalities in right hind leg.
2. Radiographs- under anesthesia for proper positioning of limbs and minimal 
discomfort to animal.
3. Further questions for owner:  origin of dog, lameness in parents, OFA 
certification of parents, any table scraps.