Learning Issues

1) What is a cranial drawer sign? What is normal, and what is expected in a 
cranial cruciate ligament 
rupture?

A positive cranial (ÒanteriorÓ) drawer sign is the pathological movement of the 
tibia cranial to the 
femur.  This movement is due to rupture of the cranial cruciate ligament.  The 
cranial cruciate ligament 
in the dog normally restricts cranial movement (cranial drawer) and internal 
rotation of the tibia in 
relation to the femur.  A diagnosis of cranial cruciate rupture is based 
primarily on elicitation of 
pathological movement during physical exam.  

An outline of the physical exam test for cranial drawer movement is below:

A. The distal femur is grasped in one hand from the caudal aspect by placing the 
thumb on the lateral 
femoral condyle and the fingers over the patella.
B.  The proximal tibia is grasped in the opposite hand from the caudal aspect by 
placing the thumb 
over the fibular head and the fingers over the tibial crest.
C. Increased cranial movement (> 3-5mm) of the tibia in relation to the femur 
indicates rupture of the 
cranial cruciate ligament; joint laxity in flexion is usually associated with 
partial tears.  
D. An alternative method of physical diagnosis involves tensing the 
gastrocnemius muscle by flexion 
of the hock while the femur is held at 90 degrees in relation to the tibia 
(tibial compression).  
Forward movement of the tibia is a positive diagnostic test for cranial cruciate 
ligament injury.

2) What types of injury could cause stifle joint pain and effusion?

Trauma resulting in: 

Cranial Cruciate Rupture Ð partial or complete
Caudal Cruciate Ligament Rupture
Stifle Joint Sprain
Meniscal Injuries
Patellar Luxation
Collateral Ligament Rupture
Traumatic Joint Luxation

3) What other types of abnormalities could cause partial weight bearing lameness 
in a hind leg?

Bilateral: hip dysplasia, myelopathies
Septic Arthritis
Osteochondritis dissecans of the femoral condyle or patella
Neoplasia Ð (synovial cell sarcoma)
Bony Fractures
Osteosarcoma
Neurogenic disorder

4) Is 4 cups of food a day of Hills Maintenance Dry a normal amount for this 
size/type of dog?

No, according to Small Animal Clinical Nutrition, the ideal weight for a female 
Lab of this age is 25-
32 kg.  Therefore, the ideal number of kcal for this dog would be 939-1130 based 
upon a RER of 1.2.  
According to The HillÕs Key to Clinical Nutrition, each cup of Adult Maintenance 
contains 365 kcal.  
This would result in Bonnie consuming a minimum of 1460 kcal per day (4 cups x 
365 kcal/cup). This is not including any snacks that she may receive. She should 
be eating a little more than 3 cups per day at the most. Therefore, Bonnie is 
consuming too many 
calories, which is a good explanation of why she is obese even with the amount 
of exercise her owner 
says she is receiving.  
 
5) What would we expect to see or learn from the joint tap?

A joint tap is a valuable aid in establishing a diagnosis of joint disease in 
canines.  It is of greatest 
value in confirming the presence of disease within a joint and differentiating 
inflammatory from 
noninflammatory disorders.  It may also provide information regarding a specific 
diagnosis. 
 
Normal synovial fluid is clear and colorless.  Cloudiness or turbidity is seen 
in any condition that 
causes RBCs or WBCs to enter the joint in great numbers.  Color change may be an 
indication of 
blood contamination or a pathologic condition.  Hemorrhage from an earlier 
puncture attempt or 
ongoing disease process results in a diffuse discoloration of the synovial 
fluid, whereas blood from a 
traumatic tap does not appear to be homogeneously mixed with the joint fluid.  A 
yellow-tinged fluid 
usually indicates previous hemorrhage into the joint and is occasionally seen in 
degenerative, 
traumatic, and inflammatory joint diseases. 

Normal synovial fluid is also very viscous.  A thin or watery consistency 
indicates that the synovial 
fluid is deficient in polymerized hyaluronic acid. This may occur following 
dilution by serum or 
through degradation by an intense intraarticular inflammatory reaction.

Common Clinical Findings with Synovial Fluid Cytology in Common Disorders are 
listed below:

Normal:  200-300 WBC/_l and < 10% PMN
Degenerative:  100-5000 WBC/_l and 0-12% PMN
Traumatic:  Variable WBC and < 25% PMN
Septic:  40,000 Ð 280,000 WBC/_l and 90-99% PMN
Rheumatoid Arthritis (erosive):  6000-80,000 WBC/_l and 20-80% PMN
Nonerosive immune-mediated:  4000-370,000 WBC/_l and 15-95% PMN

6) What are possible underlying causes that could lead to weakening of the 
cranial cruciate ligament?

Obesity 
Possible excessive amount of exercise 
Abnormal Conformation 
Cushings syndrome (hyperadrenocorticism)
Hypothyroidism
Immune-mediated disease

All of these can result in abnormal biomechanical forces being placed on 
BonnieÕs 
joints and ligaments.

7) Could osteosarcoma cause the clinical signs seen in this case?

No, osteosarcoma generally presents as a slow progressing lameness.  BonnieÕs 
lameness was sudden 
in onset which does not fit with the common clinical presentation of 
osteosarcoma.