Plan of action

The best ancillary test is to take pelvic radiographs, focusing on both coxo-femoral joints.

To confirm or deny hypothesis 3 of traumatic insult, the owners may provide more 
information by answering questions such as: is the house carpeted?  Are the stairs carpeted?  
Are there several wires or cords on the floor?  Are the childrenÕs toys lying around?  Does 
the dog tend to be clumsy?  For how much of the day is the dog at home alone?  Is the dog 
allowed free access to the entire house including the steps?  Radiographs should also make 
any fractures or soft tissue swelling in the joint area evident.

Hypothesis 2 can almost be eliminated based on the research and clinical signs already 
presented. Other forms of non-septic arthritis, including canine SLE associated arthritis, 
idiopathic non-deforming arthritis, and chronic infectious disease, all result in polyarthritis, 
especially in smaller joints, and have other physical findings including anorexia and 
lymphadenopathy which do not apply here. Canine Rheumatoid Arthritis is more common 
in small and toy breed dogs, usually involves all joints, especially smaller, more distal 
joints, causing shifting lameness, anorexia, muscle atrophy, cyclic fever, and generalized 
lymphadenopathy, so this condition, too, is unlikely to warrant further expensive, 
unnecessary testing in this patient.  Since osteoarthritis is typically accompanied by clinical 
signs including joint swelling, fibrosis, effusion, crepitus, and muscle atrophy, which are 
not evident in this patient, the clinical history and physical exam do not support the 
hypothesis.  To confirm or eliminate this hypothesis, the owner could be asked further 
questions for a more complete description of the events surrounding the onset of clinical 
signs.  Was there and opportunity for the patient to sustain trauma without the owner 
noticing?   Such a trauma would make osteoarthritis (and hypothesis 3) a greater 
consideration.  The radiographs will also reveal formation of new joint margins, joint space 
narrowing, and subchondral bone sclerosis and remodeling (including fissures) 
characteristic of osteoarthritis.

Our most likely hypothesis is number 1.  Hip displasia can be diagnosed based on 
radiographic examination under general anesthesia with proper positioning to include the 
entire pelvis and stifles.  While the patient is under anesthesia, OrtelaniÕs sign should be 
evaluated on the right hip to evaluate range of motion.  According to the University of 
Pennsylvania hip improvement program, PennHIP views measure and interpret hip joint 
laxity with three separate radiographs: distraction view, compression view, and hip 
extension view.  Hip dysplasia will show an obvious contrast between the distraction and 
hip extension views.  The compression view estimates how well the femoral head fits into 
the acetabulum.