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History and Clinical Signs of

Cruciate Ligament Rupture

Peter Muir

Introduction

Cruciate ligament rupture (CR) has been rec-
ognized since the early part of the twentieth
century. Although this condition was initially
considered a traumatic injury, during the past
25 years it has become widely accepted that
it is a complex trait disease with both genetic
and environmental contributions to the risk of
disease, with development of stifle instability
because of progressive fiber tearing in the cru-
ciate ligament complex (Bennettet al. 1988). It is
important to exclude CR before making recom-
mendations about the management of hip dys-
plasia in dogs because of the high prevalence of
CR and associated stifle arthritis in dogs with
pelvic limb lameness and hip dysplasia (Pow-
erset al. 2005).

History

Although owners will often provide a history
suggestive of trauma, careful analysis typically
reveals that the onset of lameness was either
insidious, or that lameness was observed to
develop by the owner after an incident of minor
trauma associated with normal daily activ-
ity. In a proportion of patients, owners will

provide a clear history of major trauma, such as

injury in a motor vehicle accident, suggesting

that a traumatic rupture of the cranial cruciate

ligament(CrCL)hasoccurred.Thisisrare,and

further investigation of such patients will often

reveal an avulsion fracture of a cruciate lig-

ament attachment site. Epidemiologically, this

proportion is not clearly documented, although

in medium- to large-breed dogs this incidence

appears less than 1% of patients; a very large

majority of dogs do not have a history of trauma

or contact injury. Currently, CR is considered a

progressive, acquired, degenerative condition.

Lameness in affected dogs is usually weight-

bearing and is typically worse after exercise.

The duration of lameness described by own-

ers is highly variable. Occasionally, owners may

report an audible ‘clicking’ during walking.

It is also common for dogs to be presented

for treatment because of subtle pelvic lame-

ness, which is usually continuously present and

fairly unresponsive to medical therapy with

nonsteroidal anti-inflammatory drugs. Obser-

vant owners may notice that bilateral lameness

is present, with the dog exhibiting a stiff pelvic

limb gait with weight-shifting to the thoracic

limbs. Lameness may also appear to shift from

one pelvic limb to the ipsilateral limb in patients

with bilateral CR. Such patients typically have

Advances in the Canine Cranial Cruciate Ligament, Second Edition. Edited by Peter Muir. © 2018 ACVS Foundation.
This Work is a co-publication between the American College of Veterinary Surgeons Foundation and Wiley-Blackwell.

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