ORTHOPAEDICS
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Article reprinted with the permission of DMV360, October 2015, Veterinary Medicine
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Bad Hips and Knees:
Hip Dysplasia
or a Torn Cruciate Ligament?
By Jennifer L. Wardlaw, DVM, MS, DACVS
VETERINARY MEDICINE
It can be difficult to differentiate between these two orthopedic problems. Luckily, the sit test,
among other diagnostic evaluations, can help.
Differentiating between a torn cruciate ligament and hip
dysplasia can be tricky, if not frustrating. In one study,
32% of dogs referred to a surgeon for hip dysplasia treatment actually had a torn cranial cruciate ligament.1 Let’s
review the differences between the two conditions and
how simply asking a dog to “sit” offers great clues.
CRANIAL CRUCIATE LIGAMENT TEAR
The severity of lameness depends on the severity of ligament disruption. For dogs with stable partial tears, lameness can be subtle and noted only after periods of strenuous activity. For dogs with complete tears, lameness will
initially be severe and non-weight-bearing. Then, moderate to severe weight-bearing lameness will occur.
Rupture of the contralateral cruciate ligament occurs in
37% to 48% of dogs within six to 17 months of the initial
diagnosis.1 However, ruptures can be bilateral on presentation, giving affected dogs what appears to be a neurologic, crouched walk.
In obvious cases, the keys to diagnosing cranial cruciate
rupture are a positive cranial drawer sign and tibial thrust.
But what about less obvious cases?
Physical examination
Orthopedic examination reveals various degrees of stifle pain with flexion and extension, variable crepitus, and
possibly clicking associated with a meniscal tear.
In patients with partial tears, a pain response is elicited
when the joint is in full extension. In patients with chronic
cases, muscle atrophy is notable, and periarticular fibro-
Figure 1: Sit Test in a Labrador.
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