Introduction
Dogs are prone to many different types of bone problems. This
page will focus on the arthritis that tends to occur in dogs, especially as
they age (Geriatric). Arthritis literally means
inflammation of the joint, but the term is used more generally to describe several
different processes. These include degenerative joint disease (DJD), infectious
joint disease, immune mediated joint disease, and crystal-induced joint diseases.
Many people use the term arthritis synonymously with osteoarthritis (OA), a
complex, slowly progressive, and degenerative arthritis that is characterized
by the gradual development of joint pain, stiffness, and a decreased range of
motion.
OA, the most common form of joint disease in dogs, is relatively
uncommon in cats. It can be seen in dogs of all ages, but is more commonly associated
with older pets. OA is becoming more prevalent as the longevity of our pets
increases.
As we learn more about the subtleties of feline medicine we
realize that many cats get significant problems in their lower back. This problem,
also know as feline hypersethesia syndrome, causes tremendous discomfort and
decreases the quality of life from many cats.
Please read our discussion of VOM
at the end of this page. It has made a significant change in how we
treat pets with arthritis. This is especially true for cats with
feline hyperesthesia syndrome.
Anatomy
Anormal joint is lined
with hyaline cartilage, which is the covering over the end of the bone. It provides
an almost frictionless surface for the bones to articulate, and also acts as
a shock absorber. Hyaline cartilage is comprised of chondrocytes, proteoglycans,
and collegan.
A normal joint is encased
in a fibrous structure called the joint capsule. The joint capsule helps stabilize
the joint and keeps the cartilage bathed in synovial fluid. Ligaments, which
attach bone to bone, also provide joint stability.
This
is what cartilage looks like in the knee joint. It is
glistening because it is very smooth and has a
lubricating layer over it called synovial
fluid.
This
picture is from an actual surgery on the knee of a dog
with a ruptured anterior cruciate ligament. The ridge
of bone running vertically at the left is arthritis.
Compated its roughened surface to the picture above.
Cause
The cause of this complex and multi factorial disease can be
primary or secondary. Primary OA results from normal stresses acting on abnormal
cartilage. Secondary OA is more common, and results from abnormal stresses acting
on normal cartilage, such as an unstable joint caused by canine
hip dysplasia , fragmented coronoid process, ununited
anconela process, patellar luxation, or a ruptured cruciate ligament. Some of
the factors that can cause OA include over- exercising, obesity, poor nutrition,
trauma, immune reactions, and genetic predispositions.
The radiograph on the left is from a normal shoulder
joint. The one on the right has an abnormal flap of cartilage at the
arrow. This is know as osteochondritis dissecans, and is a primary OA.
Damage to cartilage might occur as one event, or be the culmination
of many small events over years. As swelling occurs and the joint capusle becomes
stretched pain occurs. Your pet will use the joint less because of this pain,
leading to muscle atrophy and the inablity of the surrounding tendons and msucles
to support the joint. As the muscular support of the joint weakens the joint
capsule, ligaments, and cartilage become further stressed and stretched, leading
to even further pain. At this point the body releases chemicals called inflammatory
mediators, which further damage the cartilage and add to even more swelling.
It is obvious that this rapidly becomes a vicious cycle leading to debilitating
pain.
When OA progresses to the point that you notice your pet in
discomfort or pain the damage to the joint might be irreversible.
Symptoms
Symptoms are related to joint pain and stiffness. Most owners
notice a pet losing its ability to perform normally, such as a reluctance to
jump or climb stairs, or even limping. Stiffness after rest that diminishes
rapidly is a hallmark sign of OA. Dogs that will not go on extended walks or
pant excessively during a walk could also indicate OA. Symptoms can be worsened
by obesity, too much exercise, and by cold or damp conditions.
It is important to understand the intial symptoms
might be subtle. Your pet will be experiencing pain or discomfort,
yet it might not show any external signs.
Diagnosis
Signalment
OA is commonly diagnosed in older dogs and cats. Some breeds
are prone to getting it because of the conformation of their joints.
Dogs like Dachshunds have abnormally shaped long bones
that might predispose them to OA.
History
Most dogs show a reluctance to run or move about. Some will
be reluctant to go up or down stairs, or might even be limping. As the disease
progresses these dogs might be in overt pain and lose their appetite. Some
of these symptoms occur in other diseases, notably hip
dysplasia and intervertebral
disk disease. The are treated in different ways
in many cases, so a proper diagnosis
is imperative.
Physical Exam
In many cases there are no abnormalities detected during
a physical exam.Pain or discomfort might be found
by palpating a joint or pushing on the spinal cord. Dogs with longer standing
OA might show atrophy of muscles.
Diagnostic Tests
Radiography is an important diagnostic test to perform on
a dog or cat suspected of having OA. Even though a radiograph can be normal
in a pet that has OA, it is a substantial help in verifying the diagnosis
and determining the degree of involvement. There are many diseases that can
mimic the symptoms of OA, so a radiograph should be taken on every suspected
OA cause to eliminate these other causes.
This is a normal knee joint
radiographically.
This one has arthritis. The arrows point to all of the
rough edges that are indicative of OA. Compare these rough edges to the
smooth edges on the radiograph above. Also, the bone has a stronger whitish
appearance, another indication of OA.
This
dog was originally suspected of having arthritis based on
a history of soreness in the hip area. Radiographs
revealed a different story, as can be seen at the arrow
at the far left of the radiograph. The white circular
area in the bone has the potential to be many things,
some of them serious, so a biopsy is need to know for
sure.
A close-up view gives you a better idea of this dog's
problem.
This form of OA is called spondylosis, which is arthritis
of the vertebrae in the spine.
You can learn more about
the bones of the spine by going to our intervertebral
disk page.
This dog
was sore around its rear quarters when petted by the
owner. This could easily be arthritis, but as you
probably already figured out, something else was
amiss.
Did you figure out what is going on? Those
circular white objects towards the top right of the radiograph are 3
pennies in the rectum! At
least its a safe place to store your money.
A very important
differential when diagnosis OA
on a radiograph is a bone tumor. This one is on the femur (thigh bone).
The other
important differential on radiograph is a bone infection,
called osteomyelitis. The fuzzy or roughened edges at the
arrows is the infection.
Treatment
Treatment of OA initially includes correction of any underlying
primary diseases such as surgical correction of a torn ligament or arthroscopy
to remove a cartilage flap. Once any primary disease has been addressed, the
goal of treatment is to slow the progression of OA and to keep your pet comfortable.
It's important to realize that there is no cure for OA.
Most pets with OA will require some adjustment in their lifestyle.
Weight management is most important, since obese pets put unnecessary strain
on joints, leading to a more rapid progression of the disease. Excessive exercise
that leads to pain or discomfort should be avoided, but moderate exercise is
recommended. Swimming is an excellent exercise for pets that have OA and aren't
fearful of water. Most pets do best with several short, exercise periods per
day rather than fewer extended periods. Each patient will have their own unique
program of weight management and exercise, and we can help you individualize
one for you and your pet.
Drugs play an important part in the management of OA, and should
be used in combination with lifestyle adjustments. Many dogs, especially large
breeds can be stoic when it comes to pain. This means that these dogs are feeling
pain, but their outward appearance appears normal. This type of pain is easily
overlooked, and has lead to inadequate pain relief in the past. With the advent
of modern drugs to treat OA there is no longer any excuse for these dogs to
feel pain.
Chondroprotective Agents
These products typically contain precursors of cartilage
and joint fluid synthesis. They are administered orally or through injections.
Much controversy surrounds the use of chondroprotective (cartilage protecting)
agents. Little clinical research has been done to substantiate the claims
that these products have a positive effect on cartilage matrix synthesis and
that they have an inhibitory effect on the enzymes that break cartilage down.
These medications require up to 6 weeks of use before OA symptoms are diminished.
We like to use these medications first since
there are negligible side effects and they can be an aid in
preventing further deterioration of the cartilage.
Adequan
Adequan (polysulfated glycosaminoglycan) is an injectable
chondroprotective agent. Adequan incorporates into joint cartilage and inhibits
several enzymes that break down cartilage. No studies have been done in
animals other than horses and dogs, but it appears to be safe and effective
in other species including cats, rabbits, ferrets, and birds. We use it
first because of its ability to rapidly help a painful pet.
The intramuscular injections are initially given
twice weekly (every 3-4 days) for a month, then given monthly as needed. adequan
seems to be most effective when given in the early stages of OA, but is beneficial
in all stages of the disease. Side effects of adequan are much less common
than with NSAID's. If adequan works well after several months we will try
an oral chondroprotective agent called Cosequin.
Cosequin
Unlike the injectable adequan, Cosequin and other oral
joint supplements are considered nutraceuticals, or nutritional supplements,
and do not require FDA approval. Cosequin contains glucosamine and chondroitin
sulfate, agents proven to be effective at supporting and protecting joint
cartilage. Currently, Cosequin is the only veterinary product that contains
highly purified glucosamine hydrochloride and chondroitin sulfate mixed
in a specific ratio clinically proven to decrease the severity of OA. Cosequin
is given orally at an initial loading dose for six weeks, then decreased
to a maintenance dose that must be given continually. The rare side effect
that occurs is usually related to intestinal upset.
Synovi G3
One of the newer products we have to treat
arthritis has been very effective in in both dogs and cats. In
addition to glucosamine and chondroitin sulfate, it contains
Omega-3 fatty acids, antioxidants, Vitamin E, and MSM to name a
few.
NSAID'S
The non-steroidal anti-inflammatories (NSAID'S) are the most
commonly used drugs in treating OA in dogs. NSAID'S work by inhibiting an
enzyme in the inflammatory pathway, thereby providing analgesia (pain relief),
antipyrexia (decreased fever) and reduced tissue swelling.The enzyme that
is inhibited is called cyclooxygenase (abbreviated COX). This enzyme causes
an inflammatory reaction in the joint fluid that surrounds the joint.
These side effects can be minimized by using the lowest dosage
and frequency possible for your pet. Before we start your pet on NSAID'S we
perform an examination and run a baseline blood sample. Every 6 months we
will examine your pet and recheck the blood to look for any potential side
effects. This will make sure kidney and liver function is adequate.
Using NSAID'S alone is not recommended since the signs of
arthritis are masked, leading to a more active dog and a quicker progression
of disease. NSAID'S, in combination with chondroprotective agents, provide
cartilage building blocks in addition to pain relief, and may slow the progression
of OA.
Many OTC NSAID'S can be used to treat OA. These products
are readily available and relatively inexpensive. Some of the more commonly
used formulations contain aspirin, acetaminophen, or ibuprofen. Each product
has different anti-inflammatory and antipyretic properties, and each has a
different margin of safety with respect to dosing. It is very important to
consult a veterinarian before using any OTC drug on any pet, since it is estimated
that these drugs accounted for approximately 1/3 of all fatal animal poisonings.
In general, we do not recommend Tylenol or Ibuprofen in dogs because of the
potential for side effects.
All NSAID'S carry a small risk of side effects, so careful
observation of your pet while on one of these medications is important. If
they occur, the most common side effects are vomiting and diarrhea. There
might also be kidney
and liver
problems, and even bleeding.
Baby aspirin can be used in cats when administered under
a veterinarians supervision. Cats are much more sensitive to the side effects
of NSAID'S and should not be used without a veterinarian's prescription. Tylenol
is never used in cats because of its toxic effects.
Rimadyl and Etogesic
Both Rimadyl
(carprofen) and Etogesic (etodolac) are potent NSAID'S approved for use
in dogs. These products selectively inhibit the cox-2 enzyme and therefore
provide a greater inhibition of the inflammatory pathway with fewer intestinal
and kidney side effects. Both are given orally, twice daily for Rimadyl,
and once per day for Etogesic. Side effects are uncommon, although sensitive
individuals may experience mild intestinal upset. Rarely, more serious liver,
kidney, and intestinal side effects have been reported. Labradors are reported
to be more sensitive to Rimadyl than other breeds, so the use of NSAID's
in this breed should be carefully monitored. In Labradors a blood panel
should be checked to ensure proper liver function, and should be monitored
every 6 months while on this medication.
Steroids
Steroids are broken down into 2 main classes. The first,
known as corticosteroids or cortisone
(Prednisone, DepoMedrol), are very potent anti-inflammatory drugs that we
use on a daily basis for many disease processes. They are not our first choice
in treating OA in dogs since they are thought to actually speed the process
of cartilage destruction. The other type of steroids are called anabolic steroids
(Winstrol, Deca-Durabolin), which have an opposite effect to corticosteroids.
Steroid therapy in dogs is usually reserved for cases that
have become refractory to other treatments. It is also used in severe end
stage OA where a pet is suffering considerably and quality of life becomes
an issue. These pets get substantial relief from pain when we give one injection
of DepoMedrol with weekly injections of Winstrol. If there is a response we
can even use the oral version of Winstrol given on a daily basis. If there
is no response we will use Deca-Durabolin.
In cats, steroids are much safer to use than NSAID'S and
are frequently used in conjunction with chondroprotective agents to treat
OA. Cats also seem much less prone than dogs to the side effects of steroids.
Like any medication that is being used long term, monitoring blood parameters
is recommended.
Baby aspirin is also used in cats with
arthritis. It must be used only under the direction
of your veterinarian.
Veterinary Orthopedic Manipulation
(VOM)
An additional treatment
modality that has yielded great succes is called VOM.
It is a non-invasive and non-painful way to stimulate the nervous system to
help correct the problem. Through the use of VOM we can decrease the use of
the above medication in almost all cases. By decreasing the use of these medications
we help your pet live a longer and healthier life, while decreasing you medication
costs over the life of your pet.
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