Osteoarthritis is the most commonly diagnosed type of arthritis in dogs, with over 80% of dogs over the age of 8 years experiencing it. There are however 3 other types of arthritis that dogs may develop:
Immune mediated arthritis
Immune Mediated Arthritis
Immune mediated arthritis can also be called immune mediated polyarthritis (IMPA) as it usually affects more than one joint.
What does “immune mediated” mean?
The immune system is the body’s defence system, responsible for fighting off infections. In some animals however, this system can start to attack its own tissues -in the case of IMPA, it is the tissues of the joints that are attacked. There are a number of reasons this can happen, such as:
An infection that occurs elsewhere in the body
Cancer (neoplasia) elsewhere in the body
Sometimes, we can’t find an obvious cause for this immune response.
What are the signs of IMPA?
What you as an owner sees can vary, and sometimes the signs are quite vague, but your dog may be stiff, or show signs of lameness in different legs at different times. They may feel hot, and be quieter than normal. They may also be off their food. When your vet examines your dog they will often find multiple swollen joints, in different limbs, that are stiff and painful.
How is it diagnosed?
Your vet will take samples of the fluid in the joint by performing a joint tap. This fluid is sent to a laboratory where they will examine it under the microscope, and culture it for bacteria.
Your vet will probably also want to run some blood tests, and take xrays and scans, to look for the underlying causes we discussed above.
How do we treat it?
Once IMPA has been confirmed treatment includes:
Drugs that hold back the body’s immune system so it stops attacking its own joints, known as immunosuppressants
Treating any underlying cause
Rheumatoid arthritis is also driven by the body’s immune system; it is a very destructive form of arthritis causing small pits called erosions to form in the cartilage. It can affect the major joints of the limbs, gets worse as time goes on, and can be tricky to treat. Thankfully it is fairly uncommon. The exact cause of the immune system targeting the joints may not be clear, as in IMPA, making it difficult to diagnose. When joint fluid samples are taken lots of white blood cells are seen, but no germs are found.
Septic (or infective) arthritis is a form of arthritis caused by an infection in a joint. Infections are commonly caused by bacteria, but they may also be caused by fungi, yeasts, and viruses. The end result of this is that the infection causes destruction of cartilage in the joint and leads to irreversible damage.
An infection can get into a joint in a number of ways, such as:
An injury to the joint
During or after surgery to the joint
Spread from infection from the immediate surrounding area to the joint-“Seeding” of infections in other areas of the body in the bloodstream
What are the signs of septic arthritis?
It usually starts very suddenly, only affects one joint, and is very painful. The joint is generally swollen and hot to the touch. The skin over the joint may be red or discoloured.
How is it diagnosed?
Like other forms of arthritis, a vet exam is the first step. Your vet will take joint samples, and probably want to do some other tests such as blood tests, xrays or scans. The most important thing is that it is recognised, and treated, quickly.
And how is it treated?
Your dog will need antibiotics to treat this condition. However, it is important to use the right antibiotic, so it kills the bacteria. If possible, your vet will ask the lab to grow the bacteria and see which antibiotics they are sensitive to. However, some joint infections can be hard to grow and so the vet may make a choice of antibiotic based on the most common bacteria to cause joint infections. They will want to check your dog regularly, and before stopping antibiotics, to make sure they have worked properly. Your dog may need a long course of antibiotics too -up to 6 weeks, or 2 weeks after the signs have resolved. you should, however, see improvement in your dog after 5-7 days.
At the start of treatment, your dog may also undergo a joint flush. This is where sterile fluid is flushed into the joint, and the infected fluid withdrawn, to try to reduce the number of bacteria in the joint space. It may also be done using an arthroscope -a special camera and set of tools used to access the joint space -as a specialist procedure. Using an arthroscope means that larger clots of infected material can be removed, and the joint can be checked with a small camera. In any case, the most important thing is that your dog gets treated as soon as possible, as the earlier treatment starts, the less permanent damage will be done.