Front Matter

Chapter 12 Disorders of the Canine Thoracic Limb: Diagnosis and Treatment 295

Shoulder disorders

It is estimated that over 4.5 million people visit the
doctor every year for shoulder pain associated
with rotator cuff injuries (Oh et al., 2007). Rotator
cuff tears affect more than 40% of the population
over the age of 50 with an economic cost of over
US$3 billion annually (Tempelhof et al., 1999;
Mather et al., 2013). Given that such a large per­
centage of the human population has shoulder
conditions, it comes as no surprise that a substan­
tial percentage of thoracic limb lameness in dogs
involves the shoulder. Shoulder conditions are the
most common causes of lameness in working,
sporting, and performing dogs (Cullen et al., 2013).
Although shoulder injury appears to be
extremely common in both human and canine
athletes, a report has shown that the structural
and biomechanical characteristics of the joints
of quadruped animals are quite different from
those of humans (Sager et al., 2009). With the
coordinated action of over 25 muscles required
for shoulder motion, the ensuing movement is
complex, with the limb undergoing flexion,
extension, rotation, abduction, and adduction
(Marcellin‐Little et al., 2007). The potential for
muscle and tendon injuries causing perfor­
mance issues and lameness is significant when
all muscular contributions to the joint are con­

sidered (Figure 12.1). One author’s (SC) case

database reveals the most common muscle and

tendon sports‐related injuries in the canine

shoulder include subscapularis tendinopathy

(a component of medial shoulder syndrome),

supraspinatus tendinopathy, biceps tendinop­

athy, and infraspinatus myopathy.

Supraspinatus tendinopathy

Several degenerative disorders of the human

and canine supraspinatus tendon have been

identified, including rotator cuff tears, calcify­

ing tendonitis or tendinosis (microtears), and

tendinosis as a result of overuse (Fransson et al.,

2005). Tendinopathy has been adopted as a

generic descriptive term for the clinical condi­

tions in and around tendons arising from over­

use (Sharma & Maffulli, 2005).

Degeneration of the supraspinatus tendon is

thought to be a factor in the development of

rotator cuff tears in humans (Danova & Muir,

2003). Overuse is likely an important factor

in this disorder and has been supported in

animal models. In these models of repetitive

activity, the mechanical properties of supraspi­

natus tendons deteriorated as noted by a

decreased modulus of elasticity and decreased

Figure 12.1 Golden Retriever performing the weave poles and demonstrating significant shoulder abduction,
biomechanically stressing the medial compartment.

While not as common as injuries to the shoulder or elbow, injuries to the manus

(carpus, metacarpal bones, phalanges, and sesamoid bones) can be just as frustrating

and challenging to treat. Such injuries include hyperextension of the carpus, ligamen-

tous sprains, fractures, or luxations.