Page 103 - Adams and Stashak's Lameness in Horses, 7th Edition

Examination for Lameness 69

usually indicates the lame limb (Figure 2.1). This sign
can be observed at a walk and/or a trot.
VetBooks.ir viewed from the side and may or may not be associated
Joint flexion angles: Joint flexion angles are best
with alterations in the hoof flight arc and phase of stride.
One limb is compared with the other and the degree of
flexion is assessed. In some cases, horses compensate
A with an increased flexion of the unaffected limb.
Head and pelvic movement: Horses use their pelvis or
hemipelvis with hindlimb lameness similar to how they
use their head and neck with forelimb lameness. Both
are used as a method to “unweight” the lame limb, and
the amount of movement of each is often proportional
to the degree of lameness. Movement of the head and
pelvis (or hemipelvis) is best observed from the side and
P
should be correlated with gait changes. 7
Other Lameness Factors

It is generally considered that the majority of lameness
problems in horses occur in the forelimb due to the
increased weight‐bearing on the forelimbs (60%–65%)
Figure 2.2. Phases of the stride. (A) The cranial phase of the and the shock of landing that the forelimbs absorb during
stride is the half of the stride in front of the print of the opposite foot. movement. 7,35 The hindlimbs propel the horse dur­
(P) The caudal phase of the stride is the half of the stride in back of ing movement and carry less of the overall weight. This
the print of the opposite foot.
results in greater concussion to the structures of the
forelimbs. However, breed and use can alter this typical
Alterations in phase of the stride are best viewed from relationship. For instance, horses that pull carts or per­
the side of the horse. Potential causes for a shortened form events such as dressage, cutting, and reining, which
cranial phase of the stride include navicular syndrome, place greater stress on the hindquarters, often have a
joint problems such as osteoarthritis (OA), shoulder higher percentage of hindlimb lameness. Many hindlimb
problems, and bone spavin. Causes of shortened caudal lameness problems involve the hock and/or stifle. Horses
phase of the stride may include digital annular ligament within a discipline that do different activities may also
desmitis and tendonitis or tenosynovitis involving the have different limbs that are affected most commonly.
flexor tendons. 35 For instance, horses used for heading in team roping
The arc of foot flight: The arc of foot flight is usually have more problems in the right forelimb, and horses
changed when there is pain anywhere in the limb. The used for heeling have more bilateral hindlimb lameness
arc of one foot should be compared with that of the problems. Although there is considerable overlap, com­
13
opposite member when viewed from the side. In some mon lameness conditions that are associated with the
cases, the arc is changed in both forefeet (bilateral navic­ specific type of work should be suspected first (Table 2.1).
ular syndrome, laminitis, etc.) or in both hindfeet (bilat­ See Chapter 9 for further information on occupation‐
eral bone spavin). In the hindlimb, the arc may be related lameness conditions.
changed enough to cause the toe to drag when the limb It is also believed that approximately 95% of lame­
is advanced because of reduced flexion of the hock or ness in the forelimb occurs distal to the carpus. Close
35
stifle joints. Most horses exhibiting a decrease in height evaluation of the distal limb should be performed in any
of the foot flight arc also show alteration in their phase horse with forelimb lameness before considering an
of stride. For subtle alterations in the hoof flight arc of upper limb problem, unless a more proximal condition
the hindlimb, it is sometimes helpful to observe the is obvious. In the hindlimb, approximately 80% of
horse from the rear to compare the extent and duration lameness problems are thought to involve the hock or
that the horse presents the solar surfaces of both feet to stifle. Therefore, after preliminary examination of the
35
the observer. In general, the less sole that can be seen, the foot and distal limb, the hock and stifle should be closely
lower the arc of foot flight in the limb. 35 evaluated until conditions of those two regions can be
How the foot lands: When a painful condition is pre­ eliminated.
sent in the foot, the horse usually indicates the pain by Multiple other factors that may contribute to lame­
placing its weight opposite to the pain. For example, ness should also be considered. Horses that are improp­
with pain in the heel region, the horse may only toe‐ erly or irregularly shod may become lame. Surfaces that
touch. If the lesion is in the lateral portion of the sole, are too soft, too hard, slippery, or rocky may aggravate
the weight is carried on the medial side of the foot, and conformational imperfections or may be the outright
vice versa. cause of lameness. Improper conditioning resulting in
Joint extension: The degree of extension of the fetlock muscle fatigue is considered to be a common cause of
(how close the back of the fetlock approaches the ground) performance‐related injuries. Young horses in work may
during weight‐bearing is a sensitive indicator of how develop lameness problems more easily than older
much weight the horse is willing to bear on that limb. horses due to the immaturity of their musculoskeletal
Reduction in fetlock extension during weight‐bearing system. With the emphasis on racing and showing young