Diagnostic Plan


1. Take lateral and craniocaudal radiographs of the left stifle. We might see poorly mineralized osteophytes resulting from increased vascularity to the subchondral bone. We might also see a soft tissue mass, which could be indicative of a neoplasm such as synovial cell sarcoma. Also, we would radiograph the right stifle because it is not uncommon, when a patient presents with an acute lameness caused by rupture of a cranial cruciate ligament, to find a long-standing cruciate ligament injury in the contralateral leg without any history of acute lameness in that leg. Lastly, if tick-borne illness is present, radiographs will appear within normal limits.

2. Perform ultrasound evaluation of the stifle joint. This would enable us to examine the soft tissues of the stifle joint, paying particular attention to the status of the cranial cruciate ligament (which we would expect to be ruptured) as well as to the condition of the fibrous joint capsule. Additionally, we might see cartilage degeneration consistent with osteoarthritis.

3. Interpret the results of the previously performed arthrocentesis of the stifle joint. We might find significant concentrations of immune complexes in the synovial fluid. Also, due to increased capillary permeability and edema, we might see decreased viscosity and a mild increase in cellular content to approximately 5,000 white cells per cubic mm, with 70 to 80 percent lymphocytes. We might find neoplastic cells consistent with a possible synovial cell sarcoma. Lastly, if there is a tick-borne disease at work, we should see an increase in white cells, mostly neutrophils.

4. Possibly perform a serum chemistry panel. Because the dog would need to be sedated in order for us to take quality radiographs, we would offer to perform a pre-anesthetic serum chemistry profile. Such a profile might show significant concentrations of immune complexes in the serum.

5. Perform a Lyme titer and a tick titer. This would rule in/out the possibility of tick-borne diseases which cause arthritis.