All About Arthritis in Dogs and Cats (and how to spot it)
Has your dog or cat been diagnosed with arthritis? Are you confused what this will mean for your pet and what the next step is? Are they lame, stiff or slow and you are wondering if it's more than just age? Well in this series I'll answer all these questions and more. In this article, the first of three, I'll be busting a few myths to give you the facts about this disease, which animals are most at risk, how it progresses, what signs to look for and how to spot arthritis in both cats and dogs, as well as finally discussing how we can best diagnose this very common disease.
Arthritis, or more accurately osteoarthritis, is one of the most common diseases in our older dog and cat population. It is the result of a breakdown of cartilage within a joint which sets up a process of inflammation and further damage which gradually results in the painful disease of arthritis.
Which pets are at risk?
So which of our pets is at most risk of developing arthritis? We used to consider it mainly a disease of elderly large breed dogs, however as our understanding has grown, and with improvements in the recognition of pain, it has become apparent that arthritis is a condition that affects all breeds of dogs. It is also now recognised as being very common and under-appreciated in elderly cats with more than 60% of cats over the age of 12 have arthritic changes present on xrays. This is not to say that arthritis is a given in old age. There are certainly individuals who are at a greater risk of suffering from this painful and debilitating disease.
Number one on this list has to be specific breeds. As with a lot of conditions, breeding has resulted in genetic developmental and conformational abnormalities that massively predispose to arthritis. Breeds such as the Labrador and German Shepherd are prone to hip dysplasia that results in the hip joint not forming properly. Other breeds have been bred so that their legs are shortened and twisted, again resulting in abnormal joints and abnormal forces acting through them. Some may only be small dogs but a lifetime of abnormal wear will still take its toll, especially as our pets are now living longer than ever.
2. Fat Pets
Obesity is the next major issue and one that is becoming more and more of a problem with up to 54% of our dog and 59% of our cat population being overweight or obese. It has been clearly shown that an overweight dog may develop arthritis 3 years earlier than the same dog were it a healthy weight. Overweight cats are 5 times as likely to suffer lameness than healthy weight individuals.
Check out my obesity series to answer the following questions:
3. Prior Joint Damage
Other conditions that make arthritis more likely to develop include previous joint damage such as fractures, joint infection or ligament injury (with cruciate ligament injury in the knee being one of the the most common such issues). Osteochondrosis, which is a joint development abnormality in young growing large breed dogs, will also set up conditions that are ideal for the early onset of arthritis. In these latter cases the most commonly affected joints include the elbow and shoulder. This highlights the fact that arthritis can affect any joint in any leg.
Age is perhaps the final massive risk factor. We can’t turn back the clock and with our pet population living for longer than they ever have before more and more individuals are at risk from arthritis.
Arthritis: the disease + progression
Now we know who is most likely to get osteoarthritis but how does the disease develop? This is important to consider to help explain the clinical signs that we witness and to help understand the treatment options available. It also helps understand why no single treatment plan is appropriate for every individual and why a treatment plan will need to change with time.
A normal joint is made up of bone covered in a layer of cartilage, a smooth substance produced by special cells forming a matrix rich in substances known as proteoglycans and elastin fibres. As well as cartilage a joint is also lined with synovial membrane which produces synovial fluid. This is a clear sticky liquid that acts as a lubricant to the smooth cartilage. This normal joint structure allows smooth, friction free movement.
In the early arthritic joint, the surface of the cartilage becomes disrupted and breakdown of the cartilage matrix structure begins. The cartilage cells try and counteract this breakdown but aren't able to keep up with the damage being done. This breakdown results in cracking erosion and flaking of the cartilage until its full thickness is eroded and the underlying bone becomes exposed.
In response this exposed bone becomes thickened and new bone is formed in an effort to stabilise the joint. This in itself increases the inflammation in a joint resulting in a vicious circle of inflammation, cartilage breakdown, new bone formation and further inflamation. Depending on the underlying or causative problem, this process can be very rapid, taking place in a matter of months, or the process can be very slow progressing over years.
So how do we know our cat or dog has arthritis? Its easy they limp right? Well yes and no. Cats and dogs are different in how they let us know they are in pain so let us consider each in turn. Because they are a little easier to interpret lets start with dogs.
How to spot arthritis in dogs
Often the first sign is a mild, intermittent lameness or limping that happens after a particularly large amount of exercise. While this lameness may be seen at the end of the exercise period it is often not until the following morning, or that evening after a good rest, that our early arthritic dog appears stiff and lame. As the arthritis progresses the frequency as well as severity of lameness gets worse until a point where the dog is lame every day and can't exercise for more than a short period without becoming unable to muster more than a slow limp.
A hallmark of the lameness due to arthritis as opposed to lameness due to other causes is that, at least in the early stages, it is seen after a period of rest. Once the dog warms up and stretches out this lameness then disappears. The problem may also often seem worse or first appears when the weather is colder. In the advanced stages of arthritis stiffness and lameness generally becomes a more permanent feature.
It is very frustrating to hear from people that their pet is stiff and slowing down just due to age and that there is no way they are in pain. To this I say that age in itself isn't a disease and that there is a reason any animal, or person for that matter, is stiff or limping. Pain. For the truly skeptical and when I am as certain as I can be of the diagnosis I often will recommend a short treatment trial with pain killers. Owners are generally amazed at the improvement there is in their dog. Especially for a problem they hadn't appreciated in the first place.
While lameness and stiffness are the most obvious signs of the pain caused by arthritis there are more subtle behaviors our dogs exhibit to try and reduce the amount of pain they are in.
They will often refuse to exercise spontaneously. No longer rushing to the front door to greet visitors or stopping early on walks, instead choosing to plod slowly by your side rather than exploring the smells of the area. Your dog may refuse to jump into the car, climb stairs or come onto your bed at night as jumping and climbing causes them too much pain. They may struggle to get up first thing in the morning or whenever they lie down and this may be worse when they are on a slippy floor.
They may spend more time sleeping. After all it doesn't hurt so much when they are not moving. As a result of all this they may also gain weight which only makes matters worse. Behaviorally they may appear grumpy, agitated, irritable or lethargic. They may flinch when stroked and can even show signs of aggression when people especially strangers go to touch them. For the same reason they may also stop interacting with the family as much and become withdrawn.
Lets review these signs again as if your pet is showing any of them then they may very well be in pain due to arthritis and getting them checked out by your local vet would be a great idea:
Lameness or stiffness (especially after a period of rest which they then warm up out of)
A worsening problem in cold weather
A reduction in activity levels
Reduced desire to exercise
Unwilling or hesitant to jump or climb
Difficulty getting up especially on slippy surfaces
Increased time sleeping
Reduced interaction with the family
Change in behaviour
Cats feel pain too
Now let's consider cats and the signs you might notice if your cat is suffering from arthritis. Cats are the great hiders of disease and so it can be much harder to spot when they have a problem. Arthritis is no different. Cats tend to adapt their behaviour much better and as a result you may only notice signs of a problem when things are much more advanced, or if you know what to look for.
Cats are very 3 dimensional in the space they occupy, loving to jump, climb and sleep off the ground. In the early stages of arthritis they will still do all these activities but you are likely to notice them hesitating either before they jump up or as they are preparing to jump down from a height. Where possible they might also choose to get to where they want to go via a different route. An example of this would be a cat who used to jump straight up and down from a table choosing instead to go via a chair.
As the disease progresses and pain levels worsen then you will find them less willing to make the effort to jump or climb completely and so find that they stay downstairs or never sleep in their old high spots instead preferring lower and easier to access areas. They may also struggle to do other everyday activities such as using their litter tray or going through their cat flap. Just like dogs, activity levels in general will reduce with less hunting and play behaviour being shown, instead being replaced with an increased time spent asleep. Cats will also often choose to reduce their interaction with the family as a way of avoiding potentially painful situations. As a result they can also appear more grumpy when approached, even hissing or lashing out in more extreme instances.
Grooming habits is a final clue to watch out for in arthritic cats. Imagine being stiff and sore all the time. Past a certain point even the simple act of keeping clean becomes too much for even the most fastidious of cats. Their coat will become unkempt and scruffy looking. They will stop removing all of their shed coat and will start to become matted. As well as moving less, they will reducing their scratching activity and so their claws may also become overgrown. This can even be to the extent of curling round and growing into their pads which in itself is incredibly painful.
As you can imagine from the extensive discussion we've had on the clinical signs our pets with arthritis show, the main way we diagnose arthritis is from a full clinical history and determining that an at-risk individual is displaying appropriate clinical signs. When combined with a full and thorough clinical exam there is often no need for further testing to reach our diagnosis.
Examination findings may include thickened joints that creak and crunch and fail to move to the degree they would have done some years earlier, also known as a reduced range of motion. We will also get a sign that they are painful with this manipulation, although this can vary from a slight reluctance to move a joint through to trying to bite depending on the individuals temperament and stoicism. We will also see a loss of muscle mass in the affected limb. They are using it less and so the muscle wastes away.
Looking closer (reaching a diagnosis)
In our classic cases, such as the elderly stiff Labrador, this history and clinical examination will be enough to make our diagnosis and start discussing a treatment plan. It is not always this simple though. There will be times when further testing is needed to be confident and comfortable enough to make a diagnosis. This may be for several reasons such as the atypical patient, in the sense that they may be younger than normally expected or a breed that would thought to be less susceptible to arthritis.
Another trigger for further testing would be a patient where more unusual signs are present such as excessive pain, signs possibly attributable to nerve damage, patients with a high temperature or the lameness shifting between different legs and joints. A failure to respond to pain killers should also stimulate investigation.
Your feelings as our pets owner will also clearly play a role here too. We are talking about the diagnosis of a condition that will require ongoing management for the remainder of your pets lifetime. It is important that you are comfortable with the diagnostic procedure and for some that will mean xrays at an early stage even when the case seems relatively straight forward.
To get the best pictures, xrays are generally carried out under a heavy sedation or anaesthetic and will start with images being taken of the affected limb. This may be targeted to a single joint although very often multiple joints will have xrays taken of them as several will be affected in most patients. When we take our xrays, we are looking for a number of things including new bone formation around a joint in places where there would not normally be bone present. We look for a change in the density of the bone, with it often becoming thicker and so appearing whiter on xray. We look for thickening of soft tissue structures around a joint and we also look for a narrowing of the space between the bones of the joint.
While a patient is sedated or anaesthetised the opportunity is also taken to re-examine the leg as joint laxity, such as caused by cruciate ligament rupture, may only become apparent in a sedated or anaesthetised animal. As well as arthritic changes we are also looking for evidence of a different disease being the cause of the discomfort such as a slipped disc (or intervertebral disc disease) in the back. Bone cancer, joint infection and developmental problems in younger patients are other conditions that may also show up as will fractures which can be quite subtle. An absence of arthritic changes will also prompt an investigation into other causes of the clinical complaint.
If the xrays show that arthritis is present then this is all we can say. We can't tell the degree of pain an individual is in by looking at how much degeneration of the joint is present. We know that dogs and cats with only mild changes on xray can be incredibly painful where as pets with horrendous looking joints can be surprisingly comfortable. So xrays can confirm a diagnosis of arthritis but severity is assessed based on the clinical signs that our pet is showing as well as their response to the treatment program initiated.
As already suggested an alternative approach when the diagnosis of arthritis is highly likely is to give a treatment trial for around 2 to 4 weeks. This is typically with a non-steroidal antiinflamatory pain killer (NSAID), although other drug options may be more appropriate depending on your pets unique history. If a patient shows a good improvement then long term management can be discussed and if the response is poor then xrays can then be further justified.
If xrays are negative for arthritis and no other diagnosis can be made from them then additional testing will be needed. This might involve blood and urine testing or a sample of joint fluid may be taken from several joints. It may also be the time for advanced imaging techniques such as CT or MRI to be used and so it may also be the time for referral to a specialist veterinary center. Of course, this is just a summary and your vets feelings about your pet and close discussion with them will determine the best course of action to take for you and your pet.
I hope you have found this introduction to arthritis interesting and useful. In the next article I'll be discussing all of the different management strategies and drug free treatment options available for arthritic dogs and cats. In part 3, I will be covering drug treatment of arthritic dogs and cats as well as what monitoring we need to consider and what the long term prognosis is for our arthritic pets.
If you have any questions or if there is anything you would like covered in future articles then please leave a comment below. I would love to hear from you. Also grab your free pain monitoring chart by signing up to my newsletter and make sure you don't miss out on future content.
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