Plan of Action

1.	Since a joint tap was performed, I would like to see the results of that.  
Degenerate neutrophils would indicate an infectious process while nondegenerate 
neutrophils would make a general inflammatory response more likely.  
Hemorrhagic joint fluid would indicate an acute trauma or possibly erosive 
damage from a tumor.  The total protein levels in the fluid should be analyzed 
since increased protein indicates inflammation.  Also, a poor mucin clot would 
support an inflammatory process in the stifle joint.  If the protein count is 
excessively high, protein electrophoresis should be done to determine the globulin 
levels in the joint.  Auto-immune diseases directed against the collagen in the 
cruciate ligament may be a possible cause of the ligament's degeneration and 
rupture.
2.	If the joint tap shows degenerate neutrophils with other inflammatory changes, a 
joint fluid culture should be done to determine the cause of the inflammation 
(degenerate neutrophils are highly indicative of a bacterial infection).  However, 
there are no superficial wounds over the stifle and the dog is otherwise normal so 
joint sepsis is unlikely.
3.	I would like to examine "Bonnie" further orthopedically.  Is there evidence of 
medial buttressing?  This medial swelling in the area of the medial collateral 
ligament is pathopneumonic for cranial cruciate rupture.  It arises within hours of 
a partial or complete rupture.  I also would like to evaluate the stifle for evidence 
of a cranial tibial thrust.  This test is usually performed with the drawer signs 
under sedation to detect deficiencies of the cranial cruciate.  The stifle is held in 
extension while the hock is flexed.  During the hock flexion, I would look for any 
cranial movement of the tibial crest.  If the cranial cruciate ligament is damaged, 
the tensed gastrocnemius muscles are free to push the tibia forward.
4.	Radiographs would also help to determine the cause of the cranial cruciate 
deficiency.  Although the cruciate ligament cannot be seen on radiographs since it 
is a collagenous band, I would be able to see the effects of its rupture.  Stress 
radiography is done to detect cranial cruciate injuries.  With this technique, the 
cranial drawer test is performed at the time the radiograph is taken and the cranial 
movement of the tibia in relation to the femur can be more clearly seen on the 
radiograph.  With degenerative joint disease, osteoarthritis, the radiographs would 
show a decreased joint space, osteophyte production and periarticular soft tissue 
swelling.  In the stifle, the periarticular swelling is indicated by the displacement 
of the infrapatellar fat pad.  There would also be sclerotic changes in the 
subchondral bone.  Enthesophytes, bony proliferation at the site of ligament 
attachment, might also be present with osteoarthritis.  If neoplasia is the cause of 
the cruciate injury, then the radiographsmight show a calcified cartilage fragment 
in the joint space and a well-definied, round, calcified mass in the intra-articular 
space (synovial osteosarcoma).  With synovial sarcoma, there would be bone lysis 
on both sides of the joint and a mass of soft tissue containing calcified streaks.
5.	Arthroscopy is also useful to determine the extent of the cruciate ligament.  From 
the cranial drawer sign, it is unclear whether the ligament is completely or 
partially ruptured.  One study indicated that a complete rupture would cause a 
cranial drawer of about 9mm.  Bonnie's cranial drawer of the left stifle is only 4-
5mm.  Chronic joint laxity causes periarticular fibrosis, which minimizes the 
extent of the cranial drawer sign.  Arthroscopy would show just how badly the 
cruciate is injured and would help to determine the appropriate surgical treatment.  
Evaluation of the medial meniscus could also be done at this time.
6.	Also, since a cranial cruciate ligament requires surgery, I would like to do 
bloodwork to determine if Bonnie has any underlying hepatic or renal problems 
that might affect her ability to metabolize the anesthetic drugs.  Bloodwork would 
also indicate any current inflammatory processes.