WRANGLING ON THE RANGE #142
FROM HORSE ILLUSTRATED - JUNE 2005
RINGBONE
Ringbone is a common diagnosis. Horses young and old, backyard
pets and high-level athletes alike are all susceptible to the
disease. Some horses are unaffected; for others it spells the end
of life, and for those in between it's a lifetime of arthritis
with or without lameness. As a vet, if I find it on a prepurchase
exam it's a deal breaker. If I tell an owner a horse has it, it
conjures up feelings of dread even for the seasoned horseman. Do
a Google search on ringbone and you will get thousands of sites,
and there are almost that many different opinions on how the
disease develops, how to treat it and the prognosis for
soundness. Here I will add to the discussion with the latest on
ringbone.
What is Ringbone?
Ringbone is a horseman's term for osteoarthritis, or bony
arthritis, of the pastern and/or coffin joints--ringbone in the
pastern joint is called high ringbone, and in the coffin joint
low ringbone. Arthritis is any condition that causes inflammation
of the joint. Ostcoarthritis forms when the inflammation within
the joint creates enough damage that the body lays down bone in
an effort to heal the damaged tissue. Typically the bony
development occur at the joint surface or the attachment
sites of the joint capsule to the bone. Another term to describe
this type of damage to a joint is degenerative joint disease
(DJD).
The preferred veterinary terminology for high ringbone is
osteoarthritis or DJD of the proximal interphalangeal joint
(pastern joint); or in the case of low ringbone: osteoarthritis
or DJD of the distal interphalangeal joint (coffin joint). For
convenience, I will refer to the condition as ringbone.
Some also classify the type of ringbone as articulating, meaning
involving the joint surfaces, or nonarticulating, meaning not
involving the joint surface but rather the joint capsule where it
attaches to the bone. Ringbone can start out as nonarticulating
and advance into articulating. Nonarticulating is less painful
since it doesn't involve the joint surface where weight bearing
occurs and is therefore considered less serious.
The pastern and coffin joints are located in the lower limb of
all four legs. The coffin joint is a large high-motion joint
within the hoof, the next joint up is the pastern joint. The
pastern joint is a small joint that doesn't move very much but
carries a lot of weight. It is located between the top of the
hoof and the fetlock. Most people don't even realize that a joint
exists here.
How Does Ringbone Occur?
The most common cause of ringbone is abnormal stress on the
joint, causing that surface damage and subsequently bony
development. The abnormal stress can be in the form of poor
conformation, imbalanced shoeing or working on poor ground
surfaces. Base-narrow or basewide conformation, combined with a
toed-in or toed-out stance, creates increased weight-bearing
forces on the inside or outside of the joint by causing the horse
to land first on the outside or inside of the leg. These
increased forces can cause microdamage to the cartilage on the
joint surface and microtearing of the joint capsule or of the
collateral ligaments (stabilizing ligament on either side of the
joint). The body reacts to this microdamage initially as
inflammation. Inflammatory cells release toxins that create more
tissue damage and thin the joint fluid. More tissue damage
creates more inflammatory cells, and a cycle begins of increasing
damage. As the damage increases the body attempts to heal
initially with scar tissue, which then progresses into bony
development.
The length of time it takes for this to occur varies and is
dependent on many factors. The more trauma, and the more severe
the conformational abnormalities, the quicker the dis-
ease progresses. Hoof balance, proper trimming and shoeing,
footing and exercise are very big factors in this disease.
Unbalanced hooves, as well as long toe/low heel, can cause severe
stress on the joints. Shoeing a horse with shortened toes to
increase breakover decreases the stress on the joints and helps
reduce the inflammation, and can help slow the development of
disease. Hard footing increases trauma on the joints, while deep
footing increases the flexion of the joints leading to possible
overflexion and damage to the joint capsule.
Other causes of ringbone include blunt trauma or lacerations to
the joint, and osteochondritis dissecans (OCD). OCD is a
malformation of the cartilage layer during horse's formative
years - the disease leads to large flaps of cartilage within the
joint. When a cartilage flap or "chip" is present in the joint,
it creates a cycle of inflammation. In the case of trauma, a
single trauma event, such as direct hit to the joint or a
laceration, can cause the initial joint damage and start the
cycle of inflammation.
How Do We Diagnose Ringbone?
Radiographs (X-rays) of the leg are the best way to diagnose the
disease. The joint surfaces are usually very smooth, but when
ringbone is present extra bone is seen on X-ray.
But it's not always so easy. In the early stages of the disease,
the bony changes may not be so evident. Often only a small "spur"
is seen on the front of the joint, or some calcification away
from the joint surface is visible where the joint capsule or
collateral ligaments attach to the bone. Pain, and therefore
lameness, is caused by inflammation within the joint. Sometimes a
horse is more lame at this stage of the disease.
In these situations your vet must determine if the cause of
lameness is from the joint or some other disease process;
therefore it's always important to perform a thorough lameness
exam. This exam should include watching the horse move on hard
and soft ground, jogging straight and in circles. Flexion tests
and diagnostic nerve blocks are also important. Horses with
ringbone flex positive in the lower limb, meaning lameness
results when the lower limb is held in flexion for one minute and
then jogged off.
Nerve blocks are invaluable in determining the location of
(Using diagnostic nerve blocks to locate the source of lameness
is very helpful in cases where X-rays don't show obvious signs of
disease)
the pain. Once the pain has been localized to the lower leg by
response to an abaxial nerve block (block around the fetlock),
the pain can be further localized by blocking out each joint. If
low ringbone is the cause of pain, then the lameness resolves
when the coffin joint is blocked out; in cases of high ringbone,
lameness resolves when the pastern joint is blocked out.
Diagnostic nerve blocks are very important in the cases where the
X-rays are not so obvious.
The severity of the disease varies. Lameness doesn't always
correlate with radiographic changes. Some horses with mild
bony changes on radiographs are very lame and vice versa. There
are many sound horses with obvious ringbone in their pasterns.
When a horse has signiicant high ringbone it can be seen on the
front and sides of the pastern as hard lumps or a "ring" of extra
bone around the front and sides of the pastern. If the ringbone
can be seen easily it is already very advanced. Ringbone in the
coffin joint is much more significant and always causes severe
lameness since this is the higher motion joint.
As the disease advances it can spread into the joint, causing
severe cartilage deterioration and joint collapse, ending in full
fusion of the joint. During the process, the horse is severely
lame. Sometimes the lameness can become so severe that the
quality of life for the horse is very poor and humane euthanasia
is chosen.
How Do We Treat Ringbone?
Dealing with ringbone is not a single treatment but rather a
whole management scheme that is lifelong for the horse.
Everything is aimed at decreasing the inflammation in the joint
and saving the cartilage surface.
We start by trying to balance the hoof and increase the
breakover for the horse. This means making sure the hoof is level
from side to side and the toe is short so that the leg can roll
over the front of the hoof quicker, decreasing the stress on the
joints.
Next we address the inflammation in the affected joint. Often
this means injecting the joint with anti-inflammatory drugs such
as corticosteroids, along with synthetic joint fluid called
hyaluronic acid that helps replenish the existing thin, weak
joint fluid. This helps stop the disease progression and
hopefully slows down the damage to the joint surface.
Along with joint injections comes complementary therapy in the
form of supplements, exercise management and physical therapy.
Oral joint supplements given daily, such as chondroitin sulfate,
glucosamine, MSM and more recently oral hyaluronic acid, may help
the body to develop more cartilage and joint fluid.
Intravenous hyaluronic acid, called Legend I.V., and Adequan I.M.
(polysulfated glycosaminoglycan) are also used quite successfully
to preserve the joint. Legend works to produce more joint fluid
and act as an anti-inflammatory. Adequan works at the joint
surface helping the cartilage. Both are very effective and are
often used together.
Herbal supplements may be given in feed to help support the
joint. Yucca and devil's claw are common herbal
anti-inflammatories. A host of other products are available that
combine all of these ingredients as well some others not
mentioned in this article. Most appear to help, but none seem to
be outstanding in resolving pain for ringbone. Care must be given
when feeding herbal products to avoid allergic reactions or
colic. Product concentrations are often inconsistent, and many of
these herbs haven't been studied fully in horses.
Horses with ringbone do best with consistent low-level
exercise. Horses that stand excessively all day long tend to get
more inflammation in the joints and therefore more lame. Constant
walking around all day on pasture helps stimulate circulation and
decrease inflammation within the joint, therefore decreasing
lameness. The amount of exercise varies depending on the degree
of ringbone and the tolerance of the horse. Some horses with this
condition are able to maintain careers in the lower levels and
often do better if kept in a consistent work program. Soft
footing is better than hard, but too soft causes overflexion of
the joint and increased inflammation.
Physical therapy is also available for these horses. Warm therapy
helps loosen joints; liniments and wraps help support the joint.
Massage therapy, acupuncture, chiropractic and other alternative
therapies have varying degrees of efficacy, but all aim to loosen
tissue and decrease inflammation, as well as help other muscles
and joints that are compensating for the ringbone.
One promising new therapy called extracorporeal shockwave therapy
(ESWT) is proving to be very effective for horses with ringbone.
The true nature of how shockwave therapy works is still unknown,
but it is the focus of much research right now by many major
institutions.
What is known is that many horses show dramatic improvement with
ESWT, so it's become a therapy that is now being tried for a
variety of problems. For ringbone it has proven to be effective
for horses that are not too severe. I personally have seen many
horses respond to the therapy, including my own horses.
Response to shockwave therapy appears to depend on severity of
the ringbone and the aftercare. More severe cases require more
than one treatment, typically one treatment weekly for three
weeks. Many horses with less severe changes respond after only
one treatment. It also appears that if the horse returns to
regular exercise, the lameness resolves, but if the horse stands
idle for any length of time, the lameness can return. Horses with
severe ringbone don't appear to respond to this therapy. As with
all therapies, ESWT should be discussed with your veterinarian.
The Big Picture
The time between when a small spur forms and the joint fuses is
our time to help the horse with ringbone. I use a combination of
all the therapies mentioned above, and in most cases I can keep a
horse active and happy for many years before the ringbone gets
too severe. Thankfully, I haven't had too many ringbone cases
that I have had to put down, but I currently have a couple that I
know I will have to sooner or later. These severe cases are lame
but comfortable, and I usually inject their joints approximately
once a year. Each time though, it becomes harder to inject the
joint, and I know there will come a time where I won't be able to
due to the severe joint collapse and bony development.
For my ringbone patients that are doing well, I attribute it to
good management on the owner's part - essentially catching the
problem early and giving good joint support. However, I have seen
some of these horses become very lame, even with good joint
management. Unfortunately I can't predict which horses will do
well and which won't. Ringbone can affect any horse.
Riding With Ringbone
I personally own and ride a horse that has high ringbone. Though
he is no longer a performance horse, I still ride him on trail
and he is very comfortable because I give him what he needs. He
responded very well to extracorporeal shockwave therapy (ESWT),
but became lame again when I stopped riding during the winter
rains. I will do another ESWT treatment on him to see if I can
make him more comfortable. He has had joint injections, and I
give him Legend I.V. and Adequan I.M. regularly.
Initially he had a small bone spur on his pastern joint that
turned into significant ringbone over the course of about three
years. His current bony changes haven't progressed over the last
two years. On the whole this is very typical for this disease. He
has been a great lesson for me on how to manage ringbone, how to
manage the owner and that a horse with this disease can still
have a good quality of life.
Janice Posnikoff, DVM
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