Page 208 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.5 The hindlimb 183

VetBooks.ir 1.5 The hindlimb

Hindlimb lameness is common in the horse, than the head nod typical of forelimb lameness.
particularly in sport and general riding horses. This chapter concentrates largely on conditions
Riders often identify it as poor performance affecting the hock and stifle as the distal
rather than lameness, as a short stride and limb, pelvis and soft-tissue lesions are covered
increased pelvic excursion are harder to detect elsewhere in other chapters.

THE HOCK

OSTEOARTHRITIS OF THE DISTAL may be a poor correlation between the severity of
TARSAL JOINTS (BONE SPAVIN) lameness and the severity of radiographic changes.

Definition/overview Clinical presentation
Osteoarthritis (OA) of the tarsometatarsal (TMT) The onset of lameness or poor performance is often
and distal intertarsal (centrodistal) (DIT) joints gradual. Horses may present with a variety of clinical
and, less frequently, the proximal intertarsal signs ranging from a subtle change in performance
( talocalcaneal–centroquatral) (PIT) joint is the most without obvious lameness, to moderate or severe lame-
common cause of lameness involving the hindlimbs ness. Occasionally, the first sign is identified by a farrier
of mature horses. These are low-motion joints, when the horse resists having the limb flexed during
believed to act primarily as shock absorbers with shoeing. Mild cases may warm out of the lameness and
limited horizontal movement. Although it is usually
seen in mature animals, bone spavin can occur in
young Thoroughbreds, Warmbloods, Standardbreds 1.352
and Western performance horses. ‘Juvenile spavin’
is the term used for the condition in horses less than
2 years old. The incidence of the condition appears
to have little relationship to the type of horse or to
the type or amount of work it has undertaken.

Aetiology/pathophysiology
Many factors may play a role in the development and
progression of bone spavin. Normal ‘use trauma’ as
well as abnormal conformation such as ‘cow’ or ‘sickle
hock’ are believed to provoke formation of the con-
dition. Excessive compression and rotational forces
of the tarsal bones during jumps or stops and exces-
sive tension of the ligaments over the dorsal aspect
of the hock are all thought to be prominent in the
development of bone spavin. Other factors include
incomplete ossification and subsequent collapse of
the third and central tarsal bones (Fig. 1.352), septic
arthritis, fractures of the cuboidal tarsal bones and Fig. 1.352 Lateromedial radiograph of the hock in a
osteochondrosis (OCD). In Icelandic horses the dis- young foal demonstrating collapse of the central and
ease appears to have a hereditary component. There third tarsal bones.