166 Clinical Features
unilateral CR has been used to investigate the
predictive value of stifle radiography through
the evaluation of bilateral radiographs at ini-
tial diagnosis (Bleedornet al. 2011; Muiret al.
2011). Radiography is a more sensitive marker
of disease than physical examination, and
arthroscopy is a more sensitive marker than
radiography, particularly with regards to the
assessment of the severity of synovial effusion
and associated joint inflammation (Chuanget al.
2014; Fulleret al. 2014). Even very subtle radio-
graphic change, particularly synovial effusion,
is clinically relevant to the diagnosis of partial
or complete CR (Bleedornet al. 2011; Muiret al.
2011; Chuanget al. 2014; Fulleret al. 2014). Dur-
ing initial epidemiological studies of CR dis-
ease progression in dogs with unilateral CR,
the proportion of dogs developing subsequent
contralateral rupture was investigated, and this
risk was found to be about 50% at 12 months
after the initial diagnosis (Doverspikeet al. 1993;
Moore & Read 1995; de Bruinet al. 2007; Cabrera
et al. 2008; Buoteet al. 2009).
By using the Kaplan–Meier estimator, the
time to contralateral CR in dogs with unilat-
eral CR at diagnosis was studied in more detail
in three groups of dogs (Cabreraet al. 2008;
Buoteet al. 2009; Muiret al. 2011). Median time
to contralateral rupture was found to range
from 809 to 1,227 days in the three groups
(Muiret al. 2011). Subsequent contralateral rup-
ture occurred in 54% of dogs during the study
period, with an overall time to contralateral
rupture of 947 days (Muiret al. 2011). Median
time to contralateral rupture was reduced by
neutering in both male and female dogs, and
was inversely correlated to a weak degree with
tibial plateau angle (Muiret al. 2011).
To determine whether it is feasible to use
radiographic assessment of synovial effusion
and osteophytosis to make inferences regarding
fiber damage in the cruciate ligament complex,
more recent studies have examined the devel-
opment of contralateral rupture in dogs diag-
nosed with unilateral complete CR and con-
tralateral partial CR. Radiographic grading of
the contralateral stifle joint for the severity of
synovial effusion and osteophytosis at diag-
nosis is strongly predictive of the risk of CR
(Chuanget al. 2014; Fulleret al. 2014), even when
the contralateral stifle is deemed clinically nor-
mal by palpation (Fulleret al. 2014). If com-
pression of the infrapatellar fat pad extends cra-
nial to the cranial margin of the medial tibial
condyle, or leads to bulging of the caudal joint
capsule radiographically, then synovial effusion
is sufficiently severe to have obvious effects on
risk of disease progression over time (Chuang
et al. 2014; Fulleret al. 2014). Similar inferences
can be made if moderate to severe radiographic
osteophytosis is present (Chuanget al. 2014;
Fulleret al. 2014).
At initial diagnosis, the severity of stifle syn-
ovial effusion and osteophytosis is correlated
(Figure 22.1) (Chuanget al. 2014). In stifles with
partial CR and moderate to severe stifle syn-
ovial effusion or stifle osteophytosis, odds of
developing complete CR and an unstable stifle
in the next 12 months is approximately 10-fold
greater than for stifles with milder radiographic
change (Chuanget al. 2014). Time to develop-
ment of complete CR is significantly decreased
by this severity of radiographic change (Fig-
ures 22.2 and 22.3). Breed of dog, age, body
weight, gender and tibial plateau angle each
have little effect on the risk of progression of dis-
ease from partial to complete CR (Chuanget al.
2014).Magnetic resonance imaging
Recent work has determined that assessment of
stifle radiographs in dogs with CR can enable
inference to be made regarding the extent of
fiber damage in the cruciate ligament complex,
particularly the CrCL. A potential advantage of
magnetic resonance (MR) imaging is that the
cruciate ligament tissue can be assessed directly
for pathological change. MR images with suf-
ficient resolution for assessment of the cruci-
ate ligament complex are best acquired using a
3.0 Tesla magnet and isotropic sequences, such
as 3D Fast Spin Echo (FSE) Cube (Racetteet al.
2016). In dogs with normal cruciate ligaments,
estimation of CrCL volume using MRI is predic-
tive of ligament structural properties (Racette
et al. 2016). A fiber loss of 70–80% or more in the
CrCL tissue is typically seen in stifles with com-
plete CR. In the future, it is likely that this type
of assessment will also enable inference regard-
ing the risk of progression from partial CR to
complete CR.