Thirty Years of Diagnosing Cranial Cruciate Ligament Tears
Dr. Bud Siemering

Having just attended my thirtieth year veterinary class reunion, it
occurred to me that I should share my experiences with diagnosing thousands
of cruciate ligament injuries with you. Hopefully, some of these gems will
be useful.

Gem 1. Do not bother to look at or touch the patient until you have
carefully ascertained whether the lameness was historically of acute or
chronic onset. Chasing squirrels, jumping off furniture, and playing with
other dogs at the time lameness occurred should make you immediately think of
a cruciate injury. If the pet owner is not sure, work with them to help them
provide the history in the clear and factual manner you require.

Gem 2. Dogs who acutely and completely tear their cruciate will be very lame
and sometimes vocalize for the first 24 hours. Over the next week or two,
the initial pain of the injury diminishes and the dog starts bearing more
weight on the leg. This often times gives the owner the impression that the
stifle is getting better. If a partial cruciate tear has occurred, the dog
will appear to become sound even quicker and may in fact become completely
sound for a period of time. Some cats and light-weight dogs become sound
soon after the injury but the instability never goes away completely.

Gem 3. A partial or complete ligament tear never heals. I personally
believe that partial tears always end up tearing completely with time.
Clients have told me many times that their veterinarian recommended rest and
even NSAIDs to see if the ligament would heal. Rest does not make ligaments
heal. NSAIDs only reduce pain so the dog can weight bear more on the
unstable stifle. These patients inevitably go on to develop osteoarthritis
severe enough to cause lameness later in their life if not treated
surgically.

Gem 4. Dogs with partial cruciate tears may have episodes of intermittent
lameness for as long as a year. The cruciate ligament tears a little more as
time goes on and each time it does, lameness recurs. Instability leading to
recurrent lameness and osteoarthritis begins with even a 10% tear. Some of
the most arthritic stifles I have seen have come from long term incrementally
torn cruciates. I treat partial tears just as aggressively as I treat
complete tears.

Gem 5. Do not be trapped taking a pelvic radiograph of a dog with an acute
rear limb lameness and diagnosing hip dysplasia as the cause of the lameness.
Many patients have been referred to me for the surgical treatment of hip
dysplasia when in fact the history, clinical signs, and diagnosis was of a
cruciate ligament tear. Dogs with radiographic signs of hip dysplasia, no
matter how severe, can go through life with no clinical signs.

Gem 6. An acute muscle injury can mimic a cruciate tear initially. The most
common muscle injury I see in dogs is in the area of the proximal quadriceps.
These dogs are painful upon extension of the hip, but are also painful upon
palpation of the proximal quadriceps.

Gem 7. Dogs with bilateral cruciate tears can present just like dogs with
thoracolumbar disc disease.

Gem 8. There will typically be thickening of the medial aspect of the stifle
joint if a cruciate ligament tear has occurred. This thickening usually
occurs within three weeks and is almost pathognomonic for a cruciate tear. I
always start my exam of the stifles by comparing the medial aspect of both
stifles. I stand behind the dog, grasp both stifles on the cranial aspect
with the palm of my hands and palpate the medial aspect with my fingers. One
side will be thicker if there is a unilateral cruciate tear.

Gem 9. Acute cruciate tears will have mild joint effusion best detected by
palpating the synovial pouches located just medial and lateral to the
patellar ligament. Again, compare one stifle with the other.

Gem 10. How to determine if a drawer sign is present: Until you are
proficient at detecting drawer signs, put the patient in lateral recumbency
with the affected leg up. Get the patient to relax as much as possible.
While positioning yourself behind the patient, cradle the femur with your
3rd, 4th, and 5th fingers, place your index finger on the patella and your
thumb behind the femur and on the fabella. In the other hand cradle the
tibia with your 3rd, 4th, and 5th finger, and place your index finger on the
tibial tuberosity and your thumb well behind and on the head of the fibula.
With the stifle in a standing angle push the tibia cranially with your thumb
and pull it caudally with your index finger. Do not allow the femur or tibia
to rotate. Do not move the femur - keep it completely stable. As you try to
elicit the drawer sign move the stifle through various degrees of flexion and
extension. If you cannot get the patient to relax consider giving a very low
dose of acepromazine I.V. Give just enough so the patient can still walk
out of your exam room. I usually give a 70 lb dog 0.1 to 0.2 ml.

Gem 11. All puppies have cranial drawer signs - some up to 18 months of age.
The difference is when you perform a rapid drawer sign on a puppy by pushing
the tibia forward quickly it will “snap” to a quick stop. If the cruciate
is not intact the drawer sign will “mush “ to a slower stop even when you
use the same amount of force.

Gem 12. If the stifle is surgically stabilized correctly and surgery is
performed before osteoarthritis occurs, long term prognosis should be
excellent. However, I always tell the owner that, just as in human medicine,
this is a major ligament injury and I cannot make the stifle 100% normal.

Gem 13. Surgically stabilizing a stifle which has been unstable for a long
time and has a lot of osteoarthritis usually reduces clinical signs by 75%.
Most of the lameness comes from the instability.

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