AQHA November / December 2019 Magazine AQHA NOV-DEC 2019 PRINT (2) | Page 23
Locking STIFLES...
Signs can be more pronounced at the start of exercise, and
milder cases may move completely normally once warmed
up. Common signs include stumbling in the hind end (which
can lead to stumbling in the front end and occasionally
falling). Horses may have difficulty cantering in one or
both leads, and often have very awkward canter-trot and
canter-walk transitions. Horses may become hesitant
performing tasks they usually perform with ease. Because
patella locking is a mechanical issue and the degree of pain
varies, it’s important to seek veterinary advice to exclude
other problems such as spavin or ringbone – which may
also be present. Delayed patellar release can lead to
lameness in the stifle - increased friction of the patella
against the femur can cause joint inflammation, and the
patellar ligaments are sometimes strained or stretched.
Radiographs, ultrasound, scintigraphy or arthroscopy may
be needed to rule out other conditions. Fatigue in young horses and those training intensely in
cutting and dressage; lack of extended trotting work in
Western pleasure horses and exercising in an inverted or
hollowed-out position, all lead to poor patella function,
muscle tiredness, altered co-ordination and changes in
the development of the quadriceps and biceps muscles.
Hind foot balance can also be a predisposing factor - low
heels, elongated toes, upright inner hoof walls, long toe-
low heel and lack of heel contact alter the flight and arc
of the foot. To assess balance, draw a line following the
coronary band of the hind hoof over to the front leg – the
line should intersect with the front chestnut. With low
heels and long toe-low heel hoof conformation the line
will intersect closer to the elbow or even the girth region.
Veterinary xrays may be necessary to assess the position
of the coffin bone and the depth of the sole. This will help
guide hoof balance correction, trimming and wedges.
Upright conformation of the stifle is a risk factor because
the patella to sits higher and the medial trochlear ridge
is directed more forward instead of upward. Another
contributory factor is long patellar ligaments due to the
increased risk of strain and over-stretching. The release of
the patella relies upon the quadriceps and biceps to pull
it sideways and upward, so lack of fitness and reduced or
poor muscle tone in the quadriceps or biceps increases
the risk. Lack of fitness can occur in rapidly growing
horses that have not yet fully developed muscling and
co-ordination, in retired or sedentary horses, or horses
returning to work after a spell. Veterinary investigation and assessment is important
to rule out conditions such as stringhalt (which causes
exaggerated jerking movements of the hind legs), fractured
bones, foot abscesses and other causes of abnormal gait
in horses. Treatment options - may include hormone
injections, internal blisters, ligament splitting or surgery
and joint therapy. For some horses, improving fitness
and incorporating extended trot, swimming, walking and
trotting up hills (but not down), over poles and in deep,
sandy or loamy soils will get those hindquarters pumping
and can lead to resolution. Lunging, working in tight
circles and round penning are not recommended.
An altered range of motion can also occur in horses that
have a lameness due to hindlimb, hock or back pain which
lead to loss of normal quadriceps and biceps muscle tone
and changed coordination. Neurologic conditions such
as wobblers or damage to the nerves that supply the
quadriceps and biceps can lead to loss of overall muscle
tone and strength, predisposing to delayed release of the
patella. And stifle OCD can affect the gliding surface of
the patella, the trochlear ridges on the femur and the
patella itself. Corrective farriery is often beneficial - trimming the
inside wall and lateral heel extensions encourage a wider
stance and loading down the outside of the leg; raising
the heel and rounding the toe improves breakover; wedge
pads help limit the degree of stifle joint extension. For
horses that are light in condition, relief can come from
weight gain which increases the size of the fat pad that
lies beneath the patella. Ensuring protein and amino acid
intake is correct will assist muscle building and strength
and the response to training.
Sudden changes in management and exercise or a
downhill top line also increase the risk. Horses with this
conformation must extend the hind limbs further under
the body to accommodate the forward transfer of weight,
thereby increasing the likelihood for inadvertent fixation
of the patella. Insufficient foot angle can increase the
degree of pelvic limb extension, increasing the likelihood
for patellar fixation, and abnormal structure, inflammation
and pain of the stifle joints all increase the risk. It is not
uncommon to have a lameness problem somewhere else
in the limb, such as the hocks, which can be a contributing
factor in the development of delayed patellar release - in
these cases, treatment directed at several areas may be
necessary. Upward fixation of the patella is one of the main conditions
affecting the stifle – accounting for 15% of hind limb
lameness. In one study that reviewed treatments, 40%
of horses with locking stifles showed complete recovery,
and 20% had marked improvement following corrective
shoeing. Another 10% of affected horses showed
improvement when corrective trimming was combined
with weight gain and exercise.
If these don’t resolve the problem, surgery may be
required. Horses that regularly suffer from locking stifles
and don’t achieve a normal gait after a few strides may
not be safe to ride. To achieve the best outcome get a
veterinary opinion as soon as possible. F
All content provided in this editorial is for general use and information only and does not constitute advice or veterinary
opinion. The content does not consider individual circumstances, is not intended as a substitute for advice, and should
not be relied upon as advice or in place of consultation with your equine veterinarian. For full disclaimer, please refer to
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NOVEMBER/DECEMBER ISSUE 2019
PG.21