Front Matter

370 Canine Sports Medicine and Rehabilitation

limit hyperextension, cranial tibial translation,
and internal rotation (Arnoczky & Marshall,
1977). The caudal cruciate is the primary restraint
against caudal tibial translation and also helps
limit internal rotation of the tibia (Arnoczky &
Marshall, 1977; Heffron & Campbell, 1978;
Kowaleski et al., 2012). The medial and lateral
collateral ligaments serve to limit internal and
external rotation.
The menisci are crescent‐shaped, cartilagi­
nous tissues that partially divide the articular
surfaces of the joint (Figure 14.21). Menisci dis­
tribute load during weight bearing and provide
structural integrity to the stifle as it undergoes
tension and torsion. The menisci also play an
important role in joint nutrition and lubrica­
tion. Both menisci are anchored to the tibial
plateau. The medial meniscus has a firm attach­
ment to the tibia and medial collateral ligament,
while the lateral meniscus has a loose attach­
ment to the tibia and an additional attachment
to the femur. As a result, the medial meniscus
is more vulnerable to injury with cruciate
deficiency as it becomes trapped between the
condyle and plateau during subluxation.

Kinematics of the cranial cruciate‐
deficient stifle

While standing, the canine stifle is flexed, result­
ing in continuous loading of the CCL. This load

varies depending on activity level and contrac­

tion of various muscle groups. The sloping

articular surface of the tibia is called the tibial

plateau angle (TPA). TPA reference ranges

have been documented in four common canine

breeds, although this slope can vary signifi­

cantly between individual patients (Guastella

et  al., 2008). When the canine stifle is weight

bearing, the tibia is displaced forward, as the

femur slides down the slope of the tibia. The

steeper the angle present, the more significant

the resultant force acting upon the CCL.

Pathophysiology

Traumatic rupture of a healthy CCL is typically

caused by hyperextension and excessive inter­

nal rotation. More often, CCL injuries occur

when normal force is exerted on an abnormal

or degenerative joint. Proposed underlying eti­

ologies include biological and biomechanical

factors. Biological factors include development,

genetics, metabolic function, hormonal influ­

ences, infection, immune‐mediated processes,

and appropriate cellular production and turnover.

Biomechanical components include muscular

function and forces, alignment, conformation,

movement, and joint contacts and pressures

(Morgan et al., 2010; Reif et al., 2002). Because

cranial cruciate disease is generally degenera­

tive, a patient with a ruptured CCL in has a

(A) (B)

Meniscus - normal lateral

Meniscus - medial

Figure 14.21 (A) Normal lateral meniscus; note attachment to the tibia and femur. (B) Normal medial meniscus.
The curled edge is referred to as the “flounce sign” and is highly correlated with a normal meniscus.