History and Clinical Signs of Cruciate Ligament Rupture 117Figure 15.3 Photograph of the left pelvic limb of a
Siberian Husky. When checking for cranial drawer
motion in the stifle, it is important to place the fingertips
on the tibial crest, the fibular head, the patella, and the
lateral fabella to avoid interpreting compression of soft
tissue or internal rotation as cranial drawer motion.
of the stifle, as collateral ligament rupture com-
bined with cruciate ligament rupture can be a
consequence of traumatic injury to the stifle.
Cranial-caudal instability between the
tibia and femur may be identified by use of
the cranial drawer test or the cranial tibial
thrust test (Figures 15.3 and 15.4, respectively)
(Henderson & Milton 1978; Muir 1997). Dur-
ing application of these tests to the stifle, it
is important to place the examining fingers
directly on the bony prominences of the stifle,
to avoid interpreting movement of the skin and
overlying soft tissues as translation of the tibia
relative to the femur. It is often helpful to repeat
these tests after sedation or general anesthesia
of the patient to ensure that subtle instability
has not been missed on physical examina-
tion. This is particularly important in dogs
with chronic stifle arthritis. Here, periarticular
fibrosis may reduce, but not eliminate, cranial
translation of the tibia relative to the femur. It
is also important in nervous dogs with tense
muscles, where stifle instability may be less
apparent.
The cranial drawer and cranial tibial thrust
tests are best performed with the dog in lateral
recumbency and the stifle in partial flexion at a
Figure 15.4 Photograph of the left pelvic limb of a
Siberian Husky. With the stifle extended, an index finger
is placed on the tibial crest to determine whether cranial
displacement of the tibia occurs when the hock is flexed.
If cranial translation of the tibia relative to the femur is
identified, this is a positive cranial tibial thrust test and is
indicative of cranial cruciate ligament rupture.normal standing angle. Testing should be per-
formed in both flexion and extension, although
instability at any stifle flexion angle likely
reflects complete CR (Heffron & Campbell
1978).
Detection of stifle instability and cranial
translation of the tibia relative to the femur is
indicative of complete biomechanical disrup-
tion of the CrCL. In young puppies, a small
degree of cranial translation of the tibia rela-
tive to the femur of a few millimeters is normal
and is indicative of mild laxity in the ligament.
Here, the small amount of tibio-femoral trans-
lation during the cranial drawer maneuver will
come to an abrupt stop. In contrast, in dogs with
partial CR (Grade II sprain), the small degree
of tibio-femoral translation will end in a soft or
spongy stop (see also Chapter 16).
During physical examination, the stifle
should also be palpated carefully for cau-
dal drawer motion. Here, the cranial drawer
test will elicit an abrupt stop with minimal