Dogs of any breed, sex, or age can present for lameness resulting from cranial cruciate ligament pathology; however, a breed
predisposition has been reported in Labrador retrievers, Chesapeake Bay retrievers, rottweilers, mastiffs, American Staffordshire
terriers, Neopolitan mastiffs, Akitas, and Saint Bernards.12,13 Neutered males and spayed females are at increased risk compared with their intact counterparts.10,12,13 Larger breeds and obese dogs have an increased risk of cranial cruciate ligament disease.10 Cranial cruciate ligament rupture can occur at any age, but larger breeds tend to present at younger ages than do smaller
The presenting history of patients with cranial cruciate ligament pathology is varied. The onset varies from peracute after
a traumatic or athletic injury to slow and insidious, typical of cranial cruciate ligament disease. Dogs with an acute onset
of nonweightbearing lameness often improve over several weeks as the inflammation subsides, particularly with rest and nonsteroidal
anti-inflammatory drugs (NSAIDs). But point out to pet owners that this initial improvement does not indicate a resolution
of the condition. Commonly, dogs with early or minor cranial cruciate ligament pathology will initially return to near normal
function with time, rest, and NSAIDs only to present several weeks or months later with a more severe and persistent lameness.
In many cases, this history indicates progression to a complete cranial cruciate ligament rupture or the development of a
secondary meniscal injury.
Gait evaluation is used to detect lameness and confirm the limbs involved. In some instances, it can strongly direct you toward
a specific joint as the source of the lameness. Closely observing dogs standing still, walking, trotting, running, and sitting
and rising gives you a great deal of information regarding cranial cruciate ligament function and whether a problem is unilateral
or bilateral. Have a trained assistant lead the patient through the gait evaluation so you can see the appropriate gaits.
Dogs with even subtle lameness often lean away from the affected limb while standing. The degree of lameness noted at a walk
varies from no lameness to nonweightbearing. Often, lameness that is absent at a walk is evident when the dog is trotting
or running. Additionally, circling the dog around you may expose a subtle lameness because weightbearing is shifted toward
the inside leg. For example, subtle left pelvic limb lameness may be exposed when circling the patient around you counterclockwise.
Perform a sit test by having the patient sit and rise while facing away from you.14 Dogs with stifle or tarsal pathology will often abduct the affected limb while sitting to avoid the discomfort of the full
tarsal and stifle flexion necessary for normal sitting. Alternatively, some dogs will shift the affected limb slightly cranially
to diminish flexion of these joints. While you still must perform a complete orthopedic examination, this finding directs
you toward stifle or tarsal pathology as one source of the pelvic limb lameness. Dogs presented for bilateral pelvic limb
lameness often shift their weight to the thoracic limbs while sitting and rising. In fact, many dogs originally presented
for unilateral pelvic limb lameness will shift their weight similarly, which should make you highly suspicious of bilateral
pelvic limb involvement.
Figure 3 Palpate both stifles simultaneously to compare muscle mass and determine whether periarticular fibrosis, joint effusion,
and warmth are present.