98 Etiopathogenesis of Cruciate Ligament Rupture
whereby the stable stifles represent an earlier
phase of the disease process (Bleedornet al.
2011). Further studies are required to under-
stand the specific features that are present early
in the disease process and what mechanisms are
responsible for this change.
A substantial proportion of affected dogs
have partial CR with a stable stifle joint. Surgi-
cal treatment for dogs with CR has historically
focused on the elimination of joint instability,
rather than the mitigation of joint inflamma-
tion. For example, Hulse and others observed
the preservation of intact CrCL fibers during
second-look arthroscopy in 17 dogs with stable
partial tears treated by tibial plateau leveling
osteotomy (TPLO), which implied some pro-
tective effect of TPLO in these cases (Hulseet al.
2010). Cartilage damage was less severe with
an intact, functional CrCL (Hulseet al. 2010). It
would have been interesting to compare serial
synovitis scores to identify a potential relation-
ship with treatment outcomes in this study. Ulti-
mately, arthritis progression is expected with
varying degrees of associated lameness despite
stifle stabilization in dogs with CR (Girlinget al.
2006; Auet al. 2010). Whether this represents
the effects of chronic persistent synovitis or
some subtle mechanical cause is unknown.
Although mechanical instability exists in
CR stifles, a thorough understanding of the
associated joint pathology is important when
considering treatment options for individual
patients.
Conclusions
Stifle synovitis is an established feature of CR in
dogs. Synovitis occurs early during the course
of the disease, is profound, and plays a role in
the progression of joint disease and eventual
CrCL and caudal cruciate ligament fiber rup-
ture. Many similarities exist between CR, OA,
and immune-mediated or rheumatoid arthritis
that help to inform an understanding of the CR
disease mechanism. Synovial membrane evalu-
ation may facilitate identification of early fea-
tures associated with CR, assessment of dis-
ease severity, and allow for outcome assess-
ment following disease-modifying treatment.
The underlying trigger for the development of
synovitis and its mechanistic contribution to
disease progression should be a focus of future
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