Common Lameness Problems In Endurance Horses - Australian ...

COMMON LAMENESS PROBLEMS
IN ENDURANCE HORSES
By John Kohnke BVSc RDA
The major causes of lameness in endurance horses are largely related to ‘wear and tear’
injuries as a result of concussion and the cumulative loading of joints and tendons by
repetitive long distance exercise.
The incidence of lameness is reduced in a well conditioned horse that has adapted and
strengthened its musculo-skeletal structures to withstand the rigors of training. The
Arabian bloodlines used for endurance competition have been selected over many years
for their suitability and soundness for long distance exercise. Only mature horses over 5
years of age are permitted to compete in AERA rides which significantly reduces the risk
of bone and joint lameness associated with overloading during training and competition
in younger, immature horses used in racing and other horse sports.
However, the cumulative effects of many kilometres of training, particularly over hard,
concussive surfaces, compounded by conformational weaknesses, poor farriery and
nutritional imbalances, can increase the incidence of bone, joint and tendon injuries,
especially as a horse ages and accumulates 1000’s of kilometres in training and
competition. Expert health care and a well balanced diet, will ensure that many retiree
endurance horses still remain sound into their senior years.
In this review, I have grouped the common lamenesses into concussive or repetitive
“wear and tear” type injuries, those associated with conformational weakness and poor
farriery, and other common problems. Although many musculo-skeletal conditions can
occur in endurance horses, I have only included the most common lameness problems.
Lameness due to “Wear and Tear”
In most athletic horses, lameness accounts for up to 70% of lost training days or lay off
from training, and in endurance horses, concussion to the hoof structures and joints of the
lower limbs in particular, is the major cause of downtime from training. Conformational
weaknesses, such as upright pasterns and offset front cannon bones, often aggravated by
developmental abnormalities in growing horses due to dietary imbalances, increase the
risk of bone and joint overload and concussive failure.
Pedal Bone Problems
The pedal bone and the coffin joint inside the hoof capsule are subjected to a high degree
of concussion, which can result in demineralisation, arthritis and eventual lameness.
Although the condition of pedal osteitis, or inflammation of one or both of the front limb
pedal bones, is most common in immature thoroughbred racehorses, the cumulative

effects of weight bearing and concussion on compacted surfaces can lead to interference
with blood perfusion, bone dissolution with initial subtle lameness on soft surfaces that
compact under the soles Affected horses exhibit ‘shuffling’ and ‘proppy’ gait,
especially on soft surfaces which is exacerbated after concussive exercise. As the pedal
bone becomes more demineralised in more severe cases, in older campaigners, there is an
increased risk of fractures of the outer sides of the pedal bones where greatest
demineralisation and increase in vascular channelling occurs, as seen on X-ray.
Ensuring that a horse’s hooves are trimmed and shod to reduce sole contact, and fitting
underpads to horses with thin or flat soles, will help to reduce the risk and the severity of
pedal bone concussion and associated lameness. Horses that have had any previous
history of laminitis or mild founder, with any degree of downward rotation of the pedal
bones and collapse of the soles, are more prone to concussive hoof injury. It is important
that they are shod to support and protect the under surface of the sole and frog.
Although demineralization cannot generally be reversed, even by providing calcium and
bone minerals in excess relative to dietary requirements and resting the horses for
extended periods, therapy to increase blood perfusion within the hoof and pedal bone,
such as by fitting magnetic bell boots overnight, may help to slow down the progressive
demineralisation.
Navicular Syndrome and Coffin Joint Arthritis
Although “navicular syndrome”, as it is now termed, is largely influenced by genetic
predisposition, especially in horses with naturally small, contracted hooves, the
concussive effects of long distance exercise can result in vascular changes within the
navicular bone and arthritis in the associated coffin join. This progressive deterioration is
now collectively referred to as navicular syndrome, rather than navicular disease.
The navicular bone acts as a pulley implanted in the relative avascular upper structure of
the deep flexor tendon as it passes over the coffin joint to attach on the under surface of
the pedal bone. High loading forces in exercising horses of up to 40,000 Newtons (1000
lbs per square inch) are thought to restrict blood supply to the navicular bone.
Although early stage navicular deterioration is often responsive to oral vasodilating
therapy (termed isoxsuprine responsive), new studies reveal that fluid pressure
accumulates within the navicular structure to cause demineralisation and internal collapse
of the navicular body. The fluid eventually erupts through the articular surface of the
navicular bone into the coffin joint, resulting in progressive arthritic change. Early
navicular disease is recognized by a stumbling gait, especially when moving downhill,
increased wear on the toes of shoes, and a “scratchy” gait that often warms out on
exercise returning to be more obvious for 2-3 days after a ride. Horses often appear
to be “tied-up in the shoulders” because of the shortened stride length, and stand resting
on the toe of the affected hoof(s) to relieve pressure on the painful navicular bone.

The progressive deterioration and associated pain of diminished blood supply and internal
fluid accumulation, results in avoidance of heel contact, with development of higher
and contracted heels, and deeper grooves (sulci) around the frog, with a progressive
chronic lameness. Diagnosis by nerve blocks, X-rays and coffin joint anaesthesia can
help confirm navicular syndrome in chronic cases.
The use of rolled toes to hasten break-over and support to the heel area with eggbar
shoes, with or without heel wedges, will improve comfort and gait in early cases. Daily
supplementation with glucosamine based oral joint preparations (reviewed in a separate
section in this publication) can provide relief of early navicular related arthritic changes
in the coffin joint, in conjunction with therapeutic shoeing and regular hoof care.
Recently, the use of magnetic bell boots with strong magnetic fields above 1500 gauss
(Animal Magnetism, Wyong, Aust) have been observed to provide relief in early cases of
navicular syndrome, presumably by improving blood perfusion within the navicular bone
and hoof structure.
Laminitis
Laminitis caused by tearing and deterioration of the laminae attachment of the hoof wall
to the pedal bone within the hoof capsule, can occur as a result of extreme concussive
exercise, often referred historically as “road founder”. Although 80% of laminitic
conditions result from starch overload from excess grain (such as corn) or very lush
pastures (containing fructan sugars and other soluble non-structural sugars), during spring
in grazing horses, the average endurance horse in training, with a controlled diet and “fit”
body condition aided by regular exercise, is unlikely to develop a carbohydrate overlaod
type “founder” condition. Concussive exercise on hard ground at speed can result in
physical tearing of the laminae, with shortened stride and a ‘leaning back on the heels’
stance, often with an increased digital pulse. Prompt first aid with ice packs and antiinflammatories,
and rest, as prescribed by a veterinarian, will help resolve milk tearing of
the laminae in an otherwise healthy hoof.
Ring Bone
The bony growth referred to as “ring bone” associated with the pastern and coffin joints
is often a result of long term concussion, and is most prevalent in Arabian and other
breeds of horses with lightly boned and long sloping pasterns and turned out toe
conformation. Initially, peri-articular bone reaction, due to collateral ligament tearing
away from the pastern bones and bone surface (periosteal) reaction above or below the
joint, as a result of twisting and overflexion of the pastern joint, can cause shortening of
the stride and a ‘scratchy’ gait. However, continued concussion, especially when the
collateral ligaments are stretched and allow excess bone on bone movement within the
pastern joint, can lead to cartilage damage and subchondral bone pain within the pastern
joint. This results in chronic intra-articular ring bone in one or both front limbs. The
lameness associated with early peri-articular ring bone can be alleviated by judicious use
of anti-inflammatories, including DMSO and Dermcusal (Vetsearch, Australia), but if the
bony proliferation encroaches into the pastern joint, then arthritic changes develop which

often require more extensive and long term anti-inflammatory medication, and in severe
cases, retirement from competitive riding.
Side Bone
Lameness due to partial fracture of the lateral cartilages within the heel area that continue
to flex as they mineralise to bone in long distance horses over 8 years of age, can lead to
lameness in horses being worked over hilly terrain and sloping trails in training.
Diagnosis is confirmed by X-ray, and in severe cases, surgical removal of the incomplete
or fractured “side bones” is the only alternative where a horse exhibits discomfort and
lameness during training.
Fetlock Joint Sprain and Arthritis
In young performance horses, such as 2 year olds in racing, fetlock lameness is the major
cause of wastage. It results from overloading, concussion and overflexion with joint
sprain of the fetlock structures, followed by internal cartilage and subchondral bone
deterioration, leading to chronic arthritis. Conversely, in the mature endurance horse, the
incidence of fetlock sprain is generally low and related to accidental sprain on uneven
ground or a fall, rather than overflexion at speed. Aged campaigners are prone to
developing changes within all joints, including the forelimb fetlock joints, often seen
externally as joint ‘wind galls’ due to joint capsule and tendon bursa enlargement
resulting from long term “wear and tear” of accumulated long distance exercise. The use
of oral joint therapies, even as an ‘insurance’ against cartilage deterioration, have been
widely credited as a worthwhile preventative, and in the case of developing arthritic
change, fetlock support, and ‘joint foods’ are a useful form of therapy to maintain
soundness in endurance horses.
Splints
Horses with badly offset front cannon bones (“bench knees”) have a higher risk of
developing ‘high’ splints that involve the upper end of the front cannon bone under the
knee joint, because the medial splint bone (4 th metacarpal bone inside the cannon bone)
forms part of the lower knee joint surface. Initially, ‘high’ splints cause shortening of the
stride as the ligaments that attach the splint bone to the upper cannon bone shaft are torn
away from the cannon bone, as more weight is loaded onto the “bench knee” area. This
is a particular problem in a young horse being ridden over long distances, especially
downhill, when more weight is transferred to the front limbs. However, by 5-6 years of
age, the ligament attachments begin to turn to bone (ossify), attaching the upper third of
the splint to the cannon bone by a bony bridge, reducing the risk of ‘high’ splints. During
the process of developing a more permanent bony attachment, inflammation and bony
reaction can cause lameness, with shortening of the stride. Initial rest, followed by a
reduction in the level of exercise, with discomfort alleviated by cold packs and antiinflammatories
such as ‘Bute’ and topical DMSO, can help to “work out” a high splint so
that it resolves over 4-6 weeks to form a more permanent bony attachment.

Occasionally, the upper section of a splint bone can be fractured by a knock or being
tangled up with a stick when riding. Rest for 4-6 weeks, support bandaging and cold
packs are the favoured forms of therapy, relative to the degree of fracture or bone
displacement.
‘Low’ splints, which can develop on the inside or outside of the cannons, where the splint
bones become thin and are vulnerable to trauma and fracture, are not uncommon,
characterised by local swelling, pain and lameness.
Where the lower end of the splint bone is fractured, often concluded because cold packs,
rest and bandaging do not resolve the pain or discomfort within 5-7 days (X-rays can
confirm a fracture), it is best to rest the horse and apply anti-inflammatories and support
bandaging, including magnetic wraps over the area to aid bone repair.
Knee and Shoulder Joints
Because endurance horses are mature when training is commenced, the incidence of knee
and shoulder joint arthritis is generally low. However, often a ‘tying-up’ type gait that
appears to be located in the shoulders, is most commonly due to lower limb and hoof
conditions below the fetlock, seen as restricted stride and shoulder extension resulting
in a ‘scratchy’, uneven gait. Diagnosis of the location and management under
veterinary supervision is recommended. Horses with poor conformation, such as ‘back at
the knee’, ‘deviation at the knee’ or ‘over at the knee’ have a higher risk of developing
knee joint conditions and may not withstand long term training and competition.
Tendon Injuries
The structural development and load bearing capacity of elastic tendon and suspensory
ligament tissues is influenced by exercise, cumulative loading and aging, with tendons
operating almost to their functional limit and developing elastic rebound fatigue during
exercise. Once structurally formed by 5 months of age in a young horse, tendons have
very limited, if any, capacity to regenerate after injury and can only repair damaged
collagen fibrils within the tendon bundles.
The strength, mechanical strain resistance and elastic capacity of tendons are dependant
on the nutritional input, and the structural matrix organisation and loading capacity within
the tendon fibre bundles. Tendon strength and resilience is only stimulated and
maintained by progressive loading in a step-wise manner while training.
In endurance horses, sudden overloading of tendons by slipping, falls or uphill climbs
which are already suffering cumulative fatigue, is a common cause of a ‘bowed’ tendon
or tendonitis, with highest incidence in the superficial digital flexor tendon (SDFT) on the
rear of the front limbs. Traumatic injury to tendons with internal bruising by knocks and
falls is also a common cause of tendonitis and associated swelling and lameness.

It is beyond the scope of this review to fully discuss tendon injuries and their
management. However, prompt first aid to limit internal blood vessel haemorrhage when
core tendon fibres tear or rupture, or external trauma results in bruising, is paramount to
the long term repair and rehabilitation of tendons. Prompt application of cold therapy by
ice or a cold pack (cold water hosing is not ‘cold’ enough), under an elastic bandage,
repeated 3-4 times per day, and anti-inflammatories such as ‘bute’ even for minor tendon
‘bumps’ or ‘bows’, will help control internal haemorrhage and inflammation and limit the
extent of long term structural damage to injured tendon tissue. Rest and confinement to a
stable or yard, with support bandaging of the opposite limb, and ultrasound scanning of
the injured area, are important management procedures to reduce the risk of repeated
injury and assist in formulating an appropriate rehabilitation program over a 9-12 month
period. Routine icing of tendons within 5-10 minutes after exercise to remove heat and
inflammation is considered a useful aid to reducing the risk of tendon injuries in long
distance horses. Ensuring the horse has adequate heel height and avoiding long toes will
help to reduce abnormal tendon loading.
Hock Conditions
The hock joints and associated tendon and ligament structures are prone to concussive
injury, especially if inherent conformational weaknesses such as “sickle hock” or
“straight hocks” increase the direct loading or sprain forces on the hocks. Working
horses on hilly terrain increases the loading of the hock joints as horses climb, with
development of initial internal inflammation and increased joint fluid (referred to as ‘bog
spavin’), which can develop in time to out growths and bony arthritic change within the
hock joints, or ‘bone spavin’.
Hock joint arthritic changes are usually slow to develop and have an insidious,
progressive onset with restricted stride and ‘scratchy’, uneven gait which warms out on
exercise. In a horse with a hock injury, it is unwise to exercise the animal on an inclined
treadmill or swim to maintain physical fitness as the injury may be exacerbated.
Sacro-Iliac Sprain
Although back injury only accounts for 1% of lameness in working horses, back
problems are a common diagnosis for a restricted stride, lack of lateral flexion, tensing
of the backline, tail swishing and dragging the rear toes under saddle. However,
studies indicate that sprain of the sacro-iliac ligaments accounts for 50% or more of back
related lameness, followed by bruising and injury to the vertical spinal processes on the
spinal column under the backline muscles.
Strain of the sacro-iliac ligaments that attach the spinal column (sacrum) to the pelvic
girdle bone (ilium) can cause a noticeable ‘bump’ or raised area (commonly referred to as
a “Hunter’s Bump”)on the midline just behind the pin bones or ‘os coxae’ (see
illustration). When deep pressure is applied around the edges of the bump area just
behind the high part of the rump with the fingers, horses with sacro-iliac strain will dip
and attempt to ‘squat’ because of discomfort.

Sacro-iliac sprain is relatively common in horses carrying heavy weight riders, horses
with hock or other hindlimb injuries, those working on hilly terrain or resulting from a
fall, especially where the poll area shows discomfort on manipulation. Treatments for
back problems are many and varied, and there is no single beneficial therapy. Studies
indicate that chiropractic manipulation and acupuncture therapy only provide short term
relief for sacro-iliac strain.

Poles 150mm
(6”) diameter
and 2.5 metres
in length
Repeat 4-5 times
3 horse
lengths apart
Lateral movement pattern to strengthen sacro-iliac ligaments to
assist recovery and reduce overall risk of sacro-iliac sprain.
Where obvious pain and discomfort is present, an injection of long acting cortisone is
recommended, followed by controlled exercise, designed to strengthen the sacro-iliac
ligaments. Initial finger massage with a liniment over the sacro-iliac area for 3-5 minutes
prior to exercise helps to relieve discomfort and muscle spasms. This is followed by
walking the horse at an angle over 3-4 poles (150mm diameter) spaced 3 horse lengths
apart, so that it has to lift its rear legs and move its pelvis diagonally to walk over the
poles. This is repeated 4-5 times during the warm up before riding, turning in a crisscross
manner over the poles to flex the sacro-iliac each way during the walk. Once
mounted, walking and trotting in a ‘shoulder-in’ pattern each way over 200-300 metres
will help to further strengthen the sacro-iliac ligaments over a 3-4 week period and, in
most cases, will resolve this potentially chronic condition. It is possible that routine
‘shoulder-in’ exercise each way at the walk and trot during warm-up prior to training,
could reduce the incidence of this most common back injury by strengthening the sacroiliac
ligaments and lower back structures. A blanket with magnets strategically located
over the lower back may help assist blood perfusion within the sacro-iliac area when
applied overnight and aid healing and chances of long term soundness.

Summary
There are a number of common lameness conditions related to the ‘wear and tear’ on
joints and other limb structures as a result of the concussive, loading and cumulative
stress effects of long distance exercise. It is paramount for all horses being trained for an
endurance career to have good limb conformation, a sound joints and limb structures in
order to withstand long term training.
A step-wise increase in distance and speed over a 10-12 week period to ‘leg up’ and
adapt bones and joints in horses coming into training at the beginning of each season will
help to reduce the incidence of many ‘wear and tear’ injuries as joint surfaces thicken,
bone density increases and tendons strengthen by progressive loading. Regular hoof care
is essential to minimise concussion to joints and maintenance of adequate heel height and
short toe length, with correct hoof balance, will help encourage break over and reduce
limb loading on the flexor tendons and suspensory ligaments.
Sacro-iliac injury can be minimised by adopting a lateral movement pattern during warmup
exercise on a daily basis.

An earlier fracture of this inside
splint bone has caused a bony
reaction and soft tissue swelling
which will not affect long term
soundness.