Osteoarthritis
by Professor John Innes
RCVS
Specialist in small animal surgery (orthopaedics)
What is osteoarthritis?
Osteoarthritis (OA) occurs when joints fail. Joints may fail in many ways,
such as instability, fracture, abnormal development. . Features of osteoarthritis
include gradual loss of the tissue lining the joint surface (cartilage),
extra bone formation at the joint margins, and joint swelling and inflammation.
It is clear that the disease process of OA is very complex and is still
poorly understood. The biomechanics of the joint are important but so to
is the biology - it is certainly not just down to wear and tear.
Grade
0
Normal cartilage - white, glistening, smooth. View of normal elbow
cartilage through an arthroscope
Grade
4
Extreme/end-stage erosion - no cartilage remains over whole region.
View of severe elbow osteoarthritis through an arthroscope - the cartilage
is lost and the bone underneath is exposed - this is from an 11 month old
dog.
What sort of dogs are affected?
Any type of animal may be affected by OA but the common initiating factors
may vary from breed to breed. The most common joints to be affected are
the elbows, hips and knees but any joint may be affected.
What are the signs of these diseases?
OA can cause pain and lameness although in some dogs the disease may remain
clinically silent for many months or years. The signs of the disease may
appear very slowly but occasionally, more rapidly. Typical signs are stiffness,
especially after a period of rest following exercise, lameness, and an
inability to perform certain tasks (e.g. jump in to the car). Sometimes
the signs are worse in cold, damp weather (this effect is thought to be
caused by low atmospheric pressure)
How are these conditions diagnosed?
A clinical examination by a veterinary surgeon is the first step in diagnosis.
Certain clinical tests can indicate if OA is present. If OA is suspected,
radiographs (x-rays) may be necessary to confirm the diagnosis and rule
out other possible conditions.
What can be done to treat the condition?
The treatment of OA is usually aimed at managing the condition; there is
no cure. Avoiding obesity and controlled exercise are very important. Obesity
seems to exacerbate the problem and too much or too little exercise can
also aggravate matters. Medical treatment are also commonly used. Traditionally,
analgesics (pain-killers) and anti-inflammatory drugs (NSAIDs) (e.g. carprofen
[Rimadyl], meloxicam [Metacam], tepoxalin [Zubrin]) are used. These often
help relieve pain and lameness and may need to be given every day. There
are also other agents, known as slow-acting drugs, that are sometimes used
(e.g. pentosan polysulphate - Cartrophen Vet).
Nutritional supplements (e.g. glucosamine, chondroitin sulphate, omega-3
fatty acids, turmeric) are commonly used also but it should be emphasised
that there is currently little evidence to support their use. Nevertheless,
certain agents in this class may prove to be of benefit - time will tell.
At Liverpool, we are actively involved in scientific evaluation of some
of these agents.
In severe OA of the hip associated with intractable pain one might consider
a total hip replacement. This operation is similar to that performed in
people and can relieve pain and provide excellent function. Careful specialist
evaluation of the dog is required prior to such a surgery. At Liverpool
we use the Biomedtrix
canine hip system, which is probably the most widely used hip system for
dogs in the world today. Prototype joint replacements for the canine elbow
and knee are currently undergoing early clinical evaluation.
