Page 1046 - Adams and Stashak's Lameness in Horses, 7th Edition

1012 Chapter 9

(DIT) and tarsometatarsal (TMT) osteoarthritis may
progress to partial or complete ankylosis.
VetBooks.ir disease typically present with a standard history of
Western pleasure horses with distal tarsal (DIT/TMT)
hindlimb lameness and lack of propulsion. A trainer
may also specify that a horse is not “engaging” as they
are capable of. It is the authors’ subjective experience
that primary TMT‐related lameness is exacerbated with
the affected limb on the inside of the circle, while pri­
mary DIT‐related lameness is exacerbated with the
affected limb on the outside of the circle, although the
incidence of simultaneous disease is high. The TMT
joint was the most frequently blocked synovial structure
(N = 704) in the demographic review (Table 9.1).
Subsequently, the TMT joint was the most frequently
medicated synovial structure. The DIT joint was blocked
second most frequently and was the third most medi­
cated joint (Josh Donnell, Unpublished data).
In a study of 103 hindlimbs assessed with MRI, the
majority of which were western performance horses,
osteoarthritic changes of the DIT and TMT joints were
the most common findings. Other degenerative tarsal
2
changes such as subchondral cystic lesions and intertar­
sal desmopathy that were underappreciated radiograph­
ically were identified with MRI. With the increasing
2
frequency of distal tarsal/proximal metatarsal MRI
examinations, there will likely be further insight into the
range of pathologic changes that occur in this complex
region.

Stifle Disease
Similar to equine athletes of other disciplines, stifle
disease is a consistent source of lameness for western
pleasure horses. The standard clinical and dynamic
lameness exam reveals hindlimb lameness of varying
Figure 9.56. Standing stifle arthroscopy being performed with degrees with effusion typically present in both the medial
the use of an 18‐auge disposable arthroscope. This technique has femorotibial and femoropatellar joints. Unlike some of
been used on numerous western performance horses to identify the other lameness conditions, stifle disease does not
and characterize pathologic changes within the stifle. subjectively seem to be consistently worsened with the
affected limb on the inside or outside of the circle, as it
can be present during either scenario.
rehabilitation. In the western performance practice Diagnostic analgesia to investigate the source of the
demographic review, 1,212 cases received shockwave stifle lameness is standard as for other hindlimb gait
therapy to medically manage suspensory desmopathy abnormalities, with the authors routinely anesthetizing
(Josh Donnell, Unpublished data). all three joints of the stifle simultaneously to effectively
rule in or out the stifle as the source of lameness.
Anesthesia of the individual stifle joints may then be
DISTAL TARSAL DISEASE pursued at a later blocking session if warranted. Over
the 7‐year study period, all three joints of the stifle were
Pursuant to a discussion of hindlimb suspensory anesthetized 235 times, while the femoropatellar, medial
desmopathy, dialog regarding distal tarsal (hock) disease femorotibial, and lateral femorotibial joints were indi­
naturally follows thereafter as the two conditions are vidually anesthetized in 362, 100, and 57 cases, respec­
both commonly seen in the western pleasure athlete and tively (Table 9.1). Likewise, the femoropatellar joint was
often simultaneously. In contrast to horses of other dis­ the most frequently medicated stifle joint being treated
2
ciplines, a considerable frequency of juvenile (2–3 years in 5,133 cases. Overall, the femoropatellar joint was the
of age) osteoarthritis is observed in the distal tarsal second most frequently treated synovial structure behind
joints of western pleasure horses. The high prevalence of the TMT joint. The medial and lateral femorotibial
disease is attributed to the repetitive loading and tor­ joints were individually treated in 960 and 338 cases,
sional forces placed on the hocks of western pleasure respectively, while all three stifle joints were medicated
horses during the collected lope. In addition, all pivots simultaneously in 235 cases (Table 9.2).
and overall directional changes in western pleasure are Once the lameness has been localized to the stifle,
to be performed through hindlimb propulsion, of which standard diagnostic evaluation is performed both radi­
the hocks and stifles are the driving force. With age and ographically and ultrasonographically. The standard
progressing levels of work, juvenile distal intertarsal ultrasonographic assessment of the stifle should include