One of the more common problems seen in the hock that can significantly
interfere with a horse's future soundness is Degenerative Joint Disease,
commonly known as Spavin.
Spavin affects some Icelandic Horses. We understand that a veterinarian in Denmark has been attempting to find the cause of spavin in Icelandic Horses. We have seen it "dismissed" as not-an-issue when an exporter is attempting to sell a horse with spavin (or shadows on the hock x-rays). But if the buyer wants to re-sell the horse here in the US, it's worth has declined dramatically.
In an article in Eidfaxi magazine, Issue 4, 1997, entitled
"Spavin is a Serious Problem in
Icelandic Horses", the following was gleaned:
About 50% of the riding horses in Iceland, aged six to twelve years,
reacted to the flexion test or showed some changes in
The author indicated that their research showed the spavin was not caused by overuse or conformation flaws as previously thought. It would be very interesting to know how this conclusion was reached. The research done also showed that horses with higher action had no more spavin than the general numbers.
It was indicated in the study that spavin was most likely
inherited. An abstract of a study in regard to spavin and Icelandic Horses is quoted below*.
Horses with negative responses to flexions texts should not be considered saleable horses.
The article supports the seriousness of lameness due to spavin, and the fact that Icelandic Horses appear to have more spavin than trotting breeds.
If the problem is genetic, is that being addressed by the Icelandic Horse community?
With the conformation of the first prized horses, it appears that the leg conformation that leans towards spavin is being rewarded. Is this a good thing to do, knowing the problems it causes?
Or do egos, ribbons, and wins take precedence over the breeding for good conformation and good using horses?
Spavin is characterised by ossification (the bony enlargement of the bones) of the joint making up the hock joint, the
end result being a stiffening of this joint.
Bone spavin is a form of arthritis and causes inflammation, swelling, and lameness. Spavin can be caused by faulty conformation, strain, or excessive concussion. The causitive factors may also range
from sport related stress such as with trotting race horses, horses forced into extreme ventroflexion, to overworking
a carthorse. Treatments range from rest, corrective shoeing, the application of blistering ointment, to surgery.
The following are some excerpts regarding hock damage from experts in their fields. This may help solve the problem of spavin with Icelandic Horses:
Joyce C. Harman, DVM MRCVS
"As the horse's back becomes hollow or stiff, his hind legs cannot engage
properly, and the front feet tend to hit the ground heel first. Essentially
the horse is in a "parked out" position similar to that of a gaited horse.
This parked-out stance is an exaggerated example of how a horse with a
hollow back looks and moves. Unnatural strain is placed on the stifles and
hocks creating lameness or soreness..."
"It is our job to know when a horse is naturally ventroflexed and should
have a regular maintenance program to keep them strong and not over stressed
to perform their desired gait efficiently and correctly. It is also our
responsibility to know when we the riders are forcing a horse to be more
ventroflexed than necessary or to know when a horse is being asked to
ventroflex but is not meant to do so structurally.
At some point, with age and/or suspicion of stress over time one should be
aware of hock stress. X-rays in later years can help to see at what point a
horse may need special supplements to help possible bone friction or loss of
joint lubrication which can be common of those horse that are over or
improperly used. It is my experience to see some arthritic development in
horses even as young as 4 due to what is being asked of them at an early
Dr. Robert Baird:
"Horses under saddle frequently develop thickening of the spines of T18 and
L1, the two vertebrae which comprise the thoraco-lumbar joint (Figure 2).
This thickening may result in back pain and leg lameness.
Impulsion is the action of driving the basculed body forward with the
propulsive muscles of the hindquarters, not the hocks. A horse without a
bascule is a horse without impulsion. A horse without impulsion is grossly
inefficient, and is prone to injury and premature unsoundness."
Rose Miller, TWH:
"We also need to look at the pelvic slope. It
should be moderately sloped, not tending toward flat, or the horse will
'leave his hocks behind' as he travels. High hocks predispose the horse to "travel
downhill" especially if they are quite a bit higher than his knees and he
will have trouble getting his hocks up under himself."
Lee Ziegler, gaited horse judge, trainer, clinician:
"Camped-out hind legs. A horse with hocks that fall considerably behind the
plumb with his buttocks will have trouble flexing at the joints, stepping
under his body, and attaining a round position."
From Washington State University, Horse Conformation Analysis:
"Deviations of Hindleg Conformation:
Post Leg--Post leg is upright, which causes concussion in hock, predisposing
stifle problems and bone spavins. Pounding breaks down the lubricating
fluid in the hock."
From Principles of Conformation Analysis:
"Long boned hind limbs:
The downside of this construction is that if the hind limb is too
crooked--especially at the hock joint--curbs and spavins are likely, and
engagement of the hindquarter becomes difficult for the horse."
Carla Huston BES, Body Type and Proper Movement:
"In the hindlimb a common fault is cow-hocks. The horse stands base-narrow to
the hock and base-wide from the hock to the feet. The hocks point toward one
another, and the feet are widely separated. Along with being a common
conformation defect it is also one of the worst. There is excessive stress
on the inside of the hock joint and many times bone spavin is a result."
Susan Harris, Horse Gaits, Balance, and Movement:
"Cow hocks and bowed hocks are weaker than normal hocks and rotate as the horse moves; this causes grinding stress to the bones of the hock and may lead to hock ailments such as spavin."
Sara Wyche, Understanding the Horse's Back: (under construction)
*Abstract: Age-at-onset of bone spavin (BS) in horses was defined as a
double-censored survival variable. A small material of binary responses to a
radiographic examination of the distal tarsus in 439 Icelandic horses sired
by 17 stallions was analysed. In order to test different models larger
simulated data were generated according to an exponential proportional
hazard model and subject to censoring. The resulting survivor functions were
similar. The bias in survivor functions caused by double censoring in the
material was reduced by use of the self-consistency (S-C) algorithm. Using a
binary threshold model and the Weibull regression model, an analysis of
age-at-onset of spavin resulted in severe underestimation of sire variance
components in the simulated data. Survival analysis with model led to less
biased estimates. Application of this method on the real data resulted in an
effective heritability estimate of h2=0.33, which can be compared with an
estimate of h2=0.1 based on an analysis of radiographic signs (RS) using the
binary threshold model. These results indicate that the age-at-onset of RS,
which reflect the predisposition of BS, is a trait with medium-high
Back in June, there was a conference in Iceland to talk about the diseases
of the Icelandic Horse.
Spavin was a large portion of the meeting.
As previously mentioned in the Spavin Study, 23 skeletons from a thousand
years ago were found and 7 of them had spavin. That's consistant with the
current heredity figure of spavin at 33%.
There was a discussion about the lack of official reports and statistics in
Iceland about spavin.
A vet from Sweden put forth the information that spavin is three times more
common in Icelandic Horses than in other horse breeds. The information came
from a vet who works at the animal research institute, who has access to
information about all equine breeds in that country.
Discussion included medications (not helpful) and surgery for spavin (not
The interesting thing is that Holland has gotten spavin under control,
almost eradicating it within a 20 year time frame, by not allowing stallions
showing spavin to have a breeding license.
The head vet of Iceland suggests that all stallions be x-rayed; the breeding
advisor takes that a step further by including mares also. He says the
problem is money and resistance by the breeders.
Conclusions of the conference about spavin is that it can be controlled and
that only Iceland has not addressed the issue.
Bone Diseases of the Saga Horse - A 1000 Years Old Story
S. Bj÷rnsdˇttir , E. J÷rundsson and L. Arnadˇttir
The Icelandic horse has evolved as an isolated breed since the settlement of
the country in the 8th and 9th centuries. Bones from some of the first
horses that were brought to the country, the Saga -horse, have been found in
graves documented to originate from heathen times, i.e. before year 1000.
The bones are preserved at the National Museum of Iceland.
The aim of the present study was to register all bones from horses that are
preserved from heathen graves in Iceland, measure the variation in the bone
conformation, study bone diseases and to prepare a more extensive research
project on the origin of the Icelandic horse in collaboration with museums
and scientific institutions in other countries.
Preliminary results: Bones from 23 of the best preserved graves have been
registered. Obvious signs of diseases were seen in bones from 10 horses.
Seven horses had bone spavin. Two of them had also osteoarthrosis (OA) in
the lumbar vertebrae, one had OA in the lumbar vertebrae and ossifying
spondylosis in the thoracic vertebrae, and two of the horses with spavin
also had splints. Two other horses had splints and in one horse OA was found
in both lumbar and thoracic vertebrae. The age of the horses, at death, has
not yet been determined but hopefully it will be possible as some teeth are
preserved in many cases.
Bone spavin and splints are common diseases in the Icelandic horse today
although the latter condition is less studied and documented. It is,
however, an interesting observation that both diseases were also common in
Icelandic horses 1000 years ago when the use of the horses for riding and
many other environmental factors were very different from now. The serious
changes found in the spinal vertebrae were unexpected and raise questions
about the condition of the vertebrae in the horses nowadays.
Culling rate of Icelandic horses due to bone spavin.
Bjornsdottir S, Arnason T, Lord P.
A survival analysis was used to compare the culling rate of Icelandic horses
due to the presence of radiographic and clinical signs of bone spavin. A
follow-up study of 508 horses from a survey five years earlier was
performed. In the original survey 46% of the horses had radiographic signs
of bone spavin (RS) and/or lameness after flexion test of the tarsus. The
horse owners were interviewed by telephone. The owners were asked if the
horses were still used for riding and if not, they were regarded as culled.
The owners were then asked when and why the horses were culled. During the 5
years, 98 horses had been culled, 151 had been withdrawn (sold or selected
for breeding) and 259 were still used for riding. Hind limb lameness (HLL)
was the most common reason for culling (n = 42). The rate of culling was low
up to the age of 11 years, when it rose to 0.05 for horses with RS. The risk
ratio for culling was twice as high for horses with RS compared with horses
without RS and 5.5 times higher for culling because of HLL. The risk of
culling (prognostic value) was highest for the combination of RS with
lameness after flexion test, next highest for RS and lowest for lameness
after flexion test as the only finding. It was concluded that bone spavin
affects the duration of use of Icelandic horses and is the most common cause
of culling due to disease of riding horses in the age range of 7-17 years.
Links to Tables in the study:
 Distribution of causes of culling of 98 Icelandic horses [click here]
 Survival table for Icelandic riding horses, distributed by age and
RS [click here]
 Survival table for Icelandic riding horses, distributed by age
and lameness after flexion test [click here]
 Survival table, regarding to culling because of HLL, for Icelandic riding horses,
distributed by age and RS[click here]
 Survival table, regarding to culling because of HLL, for Icelandic riding horses, distributed by age and lameness after flexion test. [click here]
Perhaps the problem may be nutrition?
It seems that we do not have as much spavin in domestic Icelandic Horses in the US, altho no
studies have been performed.