296 Canine Sports Medicine and Rehabilitation
maximum stress to failure in the tendon
(Carpenter et al., 1998; Soslowsky et al., 2000).
Supraspinatus tendinopathies can be difficult
to treat and often require lengthy management
(Carpenter et al., 1998; Soslowsky et al., 2000).
Affected tendons contain discontinuous, dis
organized fibers, and typically no acute inflam
mation is detected, explaining the often‐noted
lack of response to NSAIDs. Affected tendons
that contain such fiber patterns, as noted on
musculoskeletal diagnostic ultrasound, are
seen as hypoechoic foci or core lesions (Schramme
et al., 2010). This term is now used for similar
canine tendon lesions seen on diagnostic mus
culoskeletal ultrasound. A rapidly growing
nodule develops within the supraspinatus ten
don in chronic cases, compressing the biceps
tendon and causing pain (Lafuente et al., 2009).
Cause
It appears that repeated strain injury is an
underlying cause of supraspinatus tendinopa
thy (ST). In performance dogs, repeated strain
can result from hitting the ground or agility
contacts on an outstretched thoracic limb, quick
turns, and repetitive eccentric contractions as
well as concentric contractions with the muscle
in a lengthened state. Slipping, overstretching,
and overuse of the muscle can also contribute.
Thus, dogs that perform agility are overrepre
sented in ST cases. In a recent retrospective study
of dogs affected by ST, agility dogs made up 58%
of the overall performance canine population
(Canapp et al., 2016a). Initiation of ST may in part
be due to inflammation, but inflammation has not
been seen to exacerbate the disease and was found
to be absent when evaluating histology and ten
don fibers (Canapp et al., 2016a). Additionally, that
study indicated that commonly occurring concur
rent thoracic limb pathological changes have the
potential to predispose dogs to ST. This suggests
that ST can occur as a secondary condition.
Diagnosis
Patients with supraspinatus tendinopathies pre
sent with varying degrees of lameness, from a
shortened stride length to a significant weight‐
bearing lameness. The lameness worsens with
activity and is resistant to treatment. Atrophy of
the supraspinatus muscle may be noted as well
as pain on direct palpation over the tendon with
flexion of the shoulder. ST presents unilaterally
more frequently than bilaterally (62% to 38%,
respectively) (Canapp et al., 2016a). No sex
predisposition is apparent. A retrospective study
found that dogs diagnosed with ST frequently
had concurrent elbow (55%) and/or shoulder
(62%) pathological changes (Canapp et al., 2016a).
Mineralization within the tendon or bony
remodeling at the point of insertion on the greater
tubercle or along the region of the scapular notch
to supraglenoid tubercle, may be noted radio
graphically in chronic cases (Figure 12.2). Although
MRI is an excellent diagnostic modality for acute
and chronic cases, musculoskeletal ultrasound can
be a rapid, inexpensive means of diagnosis in
the hands of experienced operators (Figure 12.3).
Musculoskeletal ultrasound allows for a definitive
diagnosis as well as serial evaluations to assess
response to treatment. Musculoskeletal ultra
sound features of ST cases are reported to include
nonhomogenous echogenicity, (93% of cases),
enlarged tendons (76%), and irregular fiber pat
terns (74%) (Canapp et al., 2016a). Less common
features include bone irregularity, bicipital teno
synovitis, and mineralization of the supraspinatus
tendon, recorded in 19%, 16%, and 15% of cases,
respectively. Identification of the core lesion was
possible in 24% of cases.
Arthroscopic exploration can be performed to
evaluate the shoulder and elbow for concurrent
conditions. Although the supraspinatus tendon
is extracapsular and cannot be directly evaluated
via arthroscopy, a supraspinatus bulge causing
biceps tendon contact/compression and a biceps
tendon kissing lesion are commonly foundFigure 12.2 Lateral shoulder radiograph showing
mineralization within the supraspinatus tendon (arrow).