Magnetic Resonance Imaging of the Stifle 161(A) (B)Figure 21.10 Sagittal (A) SE
T1-weighted MR image of a
9-year-old, intact female,
mixed-breed dog and sagittal (B)
SE T1-weighted MR image of a
2.5-year-old, neutered female
Great Dane. Note the normal
caudal cruciate ligament (CaCL,
double arrow) and cranial
cruciate ligament (CrCL, single
arrow) (A). In the other dog (B),
the CaCL (double arrow) is visible
and the CrCL is completely torn.
detected (Rubin 2005). With a chronic ligament
tear, there may be complete absence of the liga-
ment or a low-SI scar that does not have the nor-
mal morphology of the ligament (Figure 21.10)
(Rubin 2005).
Bone
Cortical bone has a uniform low SI on all
sequences: the normal periosteum is not
visible (Rubin 2005). New bone formation
(periosteal, osteophytes, enthesophytes) has an
intermediate-to-low SI, and is differentiated by
location on the bone (Rubin 2005; D’Anjouet al.
2008). The SI of yellow bone marrow is similar
to that of fat (high T1 and T2 SI), while red mar-
row has a slightly lower T1 SI (Rubin 2005; Arm-
brustet al. 2008). In dogs, the SI of the marrow
in the femoral condyles on short T1 inversion
recovery (STIR) images varies with age. At 4
months, the SI relative to fat is inhomogeneous
and intermediate-to-low: at 8–16 months there
(A) (B)Figure 21.11 Dorsal GE STIR
MR image of a 2-year-old,
neutered female Chesapeake Bay
Retriever (A) and a 2-year-old,
intact male Great Dane (B).
Compare the normal appearance
(A) to the high-SI lesions (arrows)
at the proximal and distal
attachments of the cranial
cruciate ligament (B).
is a uniformly low SI (Armburstet al. 2008). On
STIR images, high-SI lesions may be detected
in the bone marrow and be due to trauma
(blunt or repetitive), hyperemia, ischemia,
infarction, inflammation, or neoplasia (Rubin
2005).
In dogs with CR, it is common to detect vary-
ing degrees of increased SI on STIR images that
are deep to the proximal and distal attachments
of the CrCL (Figure 21.11) (Bairdet al. 1998;
Martiget al. 2007; Winegardneret al. 2007; Olive
et al. 2014). Whereas these lesions develop after
surgical resection of CrCL, they have also been
observed in dogs with a partial CR or an intact
CrCL (Winegardneret al. 2007). This observa-
tion suggests that multiple pathogeneses are
possible, and questions whether the surgical
model of osteoarthrosis is the best representa-
tion of CR in dogs. Additionally, the location
of high-SI lesions is different compared to
people with anterior cruciate ligament rupture,
which further suggests a different or multiple
pathogeneses.