A therapist or a veterinarian will perform the drawer test using their hands. The test is positive if the tibia slides too far forward.
Faced with a life-altering diagnosis, whether temporarily or for the rest of the dog’s life, we look for ways out. “Maybe it is something else, something that will go away on its own.”
I was in the same boat when the vet suspected an ACL injury as a reason for Jasmine’s limp. All I wanted was a different diagnosis.
No wonder I felt for a friend of mine, asking whether there was such a thing as a false positive drawer sign. Is there?
Diagnosing CCL injuries
Your veterinarian might diagnose cruciate ligament injury based on a physical evaluation. The two things their look for are:
- joint swelling or thickening
- instability of the stifle
The two tests your veterinarian might perform to evaluate stifle stability likely are:
- cranial drawer test
- tibial compression test
Tibial compression test
The tibial compression test—cranial tibial thrust—is useful because it mimics what happens in the knee when the dog walks. If there is CCL damage, the bone moves forward when the hock is in the flexed position. This makes it different from the drawer test, a motion that doesn’t happen in real life.
Further, this test is more accurate and reliable. Yet, the tibial compression test isn’t as familiar as the drawer sign.
Further information: Diagnosis of Cranial Cruciate LigamentIinjury in Dogs by Tibial Compression Radiography
The drawer sign
A drawer sign, or drawer test, is a diagnostic manipulation to determine CCL injury in a dog’s knee. Generally, If there is any abnormal movement in the joint, the test is positive.
Take a quick look at a dog’s knee anatomy. The joint parts don’t nest within each other, such as in the hip joint. Rather, one part is pretty much sitting on top of the other. Ligaments within the knee contribute to joint stability.
The anterior/cranial cruciate ligament ACL/CCL and the posterior cruciate ligament are the two ligaments that are crucial to knee stability. One is holding the joint parts in place front-to-back and the other back-to-front. The ACL/CCL ligament is susceptible to tearing.
During the drawer test the veterinarian with stabilize your dog’s femur (thigh bone) with one hand while manipulating the tibia (shin bone) with the other. If the tibia moves forward—known as a positive drawer because of the way the bone moves similar to a drawer being opened—the ligament is ruptured.
DogKneeInjury.com
Positive drawer test
The test is positive if the tibia slides too far forward. Picture it as pulling a drawer from a chest or cabinet. The test is positive if the veterinarian can manipulate the knee in that way.
The ligament damage grades 0-5 according to the amount of excessive tibial movement in millimeters. Here is what the scoring means:
- 0 means no tear
- 1-2 indicates a partial tear
- 3 is partial to nearly-full
- 4-5 indicates full tears
False-netagive cranial drawer test
Your veterinarian might not always be able to get a positive result, especially in a lucid dog. The inability to elicit the drawer sign, unfortunately, doesn’t rule out ligament damage.
Many dogs need to be sedated before the presence of the drawer sign can be ruled out.
False-positive tests
It appears that the tibial compression test is superior to the more popular drawer test. The drawer test is more likely to have false-negative results. Further, according to the study below, it can have false-positive results as well.
Based on those results, there is indeed such a thing as a false-positive drawer test.
Further information: Diagnosis of Cranial Cruciate LigamentIinjury in Dogs by Tibial Compression Radiography
Summary
The easiest way to confirm whether there is indeed damage to the stifle ligament seems to be following the drawer test by the tibial compression test. Radiographs can further assist in confirming the diagnosis. The one thing you do not want is to have your dog undergo surgery that is not necessary.
There are more advanced diagnostics that can provide a definite picture of the state of the ligament such as MRI or arthroscopy. However, those are both expensive and invasive.
Still, though, the rule applies, measure twice and cut once.
Related articles:
Talk To Me About Dog ACL/CCL Injuries: My Dog Ruptured Their Cruciate Ligament
Canine Cranial Cruciate Ligaments: Hanging by a Thread? Stabilizing Forces in the Canine Stifle
Dog CCL Injury Grading
Dog Knee Injuries: Why The Second CCL Often Goes Too
Further reading:
Canine Cranial Cruciate Disease: Updating Our Knowledge about Pathogenesis & Diagnosis