37

Progression of Osteoarthritis

after Stifle Stabilization

Surgery

Susannah J. Sample

Introduction

The relationship between cruciate ligament
rupture (CR) and osteoarthritis (OA) is com-
plex, dynamic, and poorly understood. Histor-
ically, development of OA in clinical patients
was perceived to be a consequence of a loss
of joint stability associated with cranial cruci-
ate ligament (CrCL) fiber rupture. More recent
studies have indicated that, while joint instabil-
ity resulting from CrCL fiber tearing increases
development of OA, initiation of OA within a
diseased stifle joint actually precedes clinically
detectable joint instability. This suggests that
CrCL fiber disruption is, at least in part, a conse-
quence, rather than a cause, of the disease pro-
cess that leads to stifle OA.

Use of cranial cruciate ligament
transection as a model of osteoarthritis

The historic view that OA in canine patients
with naturally occurring CR is purely a conse-
quence of stifle instability is, in part, based on
dog model studies of CrCL transection. While
the development of OA in patients with natu-
rally occurring disease is likely more complex,

it is important to consider the consequences of

stifle joint instability on the development and

progression of OA.

After transection of the CrCL, changes occur

throughout the tissues of the synovial joint.

The articular cartilage undergoes a dramatic

anabolic response, with increased cellular activ-

ity and mitosis resulting in increased matrix

synthesis and an overall increase in tissue mass

(Adams & Brandt 1991). However, this anabolic

activity is countered by increased catabolic

activity with degradation of the collagen net-

work (Fernandeset al. 1998) and increased activ-

ity of enzymes degrading the major proteogly-

can, aggrecan (Inneset al. 2005). The result of

this proteolytic activity is to deplete the carti-

lage of aggrecan, initially in the superficial zone,

and to disrupt the collagen network. Thus, the

compressive stiffness and the tensile strength

of the cartilage are both reduced. In a stifle

affected by CR, the consequences of cartilage

degradation can often be seen during arthro-

scopic assessment, as reflected by a decrease in

cartilage stiffness and eventual fraying (Figure

37.1). Continued enzymatic activity over many

months leads to loss of tissue, such that there

may be full-thickness cartilage lesions within 3

to 5 years (Brandtet al. 1991).

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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