Photo by Michael Durham, courtesy of the Oregon Zoo
What do typos and a basketball-playing sea otter have in common? Joints.
No, I’m not talking about the smoking of a certain federally-illicit plant. The connection between my typing difficulties and the video of a marine mammal hoops star from the Oregon Zoo lies in a disease that’s common to all vertebrates – arthritis.
Arthro– refers to the joint, the spot where two bones meet; –itis, as you might remember, means inflammation. Ergo (yes, more dead languages), arthritis = inflammation of the joint or joints.
An alternate term for arthritis – degenerative joint disease or DJD – reflects a slightly sinister reality. Inflamed joints enter a cycle of inflammation and deterioration, producing a more or less inevitable decline in joint health. Fun thought, isn’t it? My winter-stiff fingers are having a party even as I type this paragraph.
To understand what goes on in an arthritic joint and how we try to manage the condition (please note the word “manage;” it will be important later), you need a good idea of the structure of the joint and the process of inflammation and degeneration.
In vertebrates (the bony ones anyway; I’m not sure about sharks and rays), most joints come in a couple of forms – high motion (think elbow) and low motion (between some of the vertebrae). Your basic joint structure involves the ends of the involved bones. These are covered in a layer of cartilage which acts as a cushion for the bone, and reduces friction, sort of like brake pads. These cartilage-covered bones are connected to each other by ligaments and by a joint capsule which wraps around the whole apparatus. The inside of the joint is filled with synovial fluid (also called joint fluid). The synovial fluid lubricates and cushions the joint and also carries nutrients and white blood cells which help fight infection.
These components keep a happy, healthy joint moving like a well-oiled machine. (forgive the cliché; it’s actually a really good analogy for how things work.) However, the body is a mechanical apparatus of sorts, and just as in a machine, a problem in one system can cause other things to be thrown off-kilter.
Any number of things can spark an inflammatory cycle within a joint. These causes include (but aren’t limited to):
- Mechanical damage
- Trauma – fractures, damage to the tendons, ligaments, joint capsule, or meniscus (a soft-tissue pad in the stifle or knee joint), penetrating wounds.
- Poor or altered biomechanics – (Wear and tear). Examples of this would include animals with abnormal conformation for their breed/species (dwarf breeds, hip dysplasia, pigeon toed, club-footed, cow-hocked, etc.); hooved animals with inappropriate trimming or shoeing; extensive work on uneven surfaces; athletics requiring repetitive strain on the joints; obesity, and prolonged confinement.
- Infection – from blood-borne systemic infections (often in newborns) or from wounds that penetrate the joint
- Immune dysfunction – in cases of autoimmune disease, the body’s own immune cells may attack the joints (rheumatoid arthritis is an example of this in humans.)
An inflammatory trigger does several things in the joint.
- It causes the release of chemicals and enzymes (inflammatory mediators) and a corresponding influx of white blood cells. These cells and chemicals are designed to kill foreign invaders such as bacteria. However, their weaponry is a little non-specific, and the chemicals that are released can also do a number on joint cartilage. As you might imagine, damage to the cartilage causes inflammation.
- It causes a decrease in the viscosity (slippery-ness) of the joint fluid. The thinner, more watery fluid is less able to minimize friction between the surfaces in the joint, resulting in cartilage damage and … inflammation.
- As the cartilage becomes damaged, it is less able to cushion the underlying bone which causes changes in the structure of the bone. This alters the movement of the joint, producing more friction, more wear and tear, and (say it with me now), MORE INFLAMMATION.
I’m sure you can guess where this is headed. Arthritis (remember, it’s called degenerative joint disease for a reason) is pretty much the epitome of a vicious cycle.
So, how does this cycle look to the patient?
- Pain – This can range from stiffness to aching to crippling agony. Needless to say, it impairs motor function.
- Weight gain – if you aren’t moving, you aren’t burning calories. Unless you manage to cut your intake, you get heavier. Weight gain alters biomechanics. Increased weight=increased load on the joints=increased wear and tear. This brings us back to symptom 1.
- Swelling – severely inflamed joints, especially those suffering from infection or an autoimmune cause, can become swollen as the amount of joint fluid increases. This distends the joint capsule, taking us again back to 1.
You may have noticed that I didn’t list old age as a cause of arthritis. What’s up with that??
Good catch. Age, in and of itself, is not a disease or a cause of disease. However, certain diseases worsen or seem to crop up in old age, and arthritis is one of the biggies. A hypothetical perfectly healthy, perfectly constructed joint with no external insult would last the life of the animal with no arthritis. However, perfection is rare in nature, and few animals move only in the ideal way with no tweaks, bumps, or strains. Degeneration, by definition, occurs over time, and age is, also by definition, a measurement of time. Ergo, as animals (including human animals) advance in age, any existing joint deterioration advances along with them.
Sadly, and boy would I like to be wrong, there is no cure for arthritis. Once the wheels are set in motion, the damage can’t be reversed – cartilage heals poorly, if at all, and once bone has changed, it doesn’t change back without surgical intervention. We talk about “managing” arthritis for a reason. The goal is to slow the cycle of deterioration and minimize the accrued damage.
Animal athletes, like human athletes, place significant stress on their joints. Over time, the increased forces from jumping, racing, high-speed stops and turns, can drive a fair amount of wear and tear on the joints. These animals often require extra care in the early stages of the cycle to minimize the damage before it gets going.
Veterinarians use a variety of tools to manage arthritis in our patients. Let’s open up that toolbox and take a look.
- Systemic anti-inflammatory medications – these drugs are often given once or twice a day and usually fall into one of two categories:
- NSAIDs (non-steroidal anti-inflammatory drugs) – these drugs act against specific enzymes in the inflammatory cascade called the COX enzymes (LINK). Examples include: ibuprofen for people, carprofen for dogs, and phenylbutazone for horses.
- Corticosteroids – These are the big guns for interrupting inflammation. Systemic examples include prednisone and prednisolone. Since corticosteroids can have profound effects on other body systems they’re usually used to manage more severe arthritis.
- Joint injections – if only one or two joints are affected, the veterinarian may suggest injecting medication such as a corticosteroid or a drug related to the molecules that make up joint fluid directly into the joint.
- Diet – this references both what the animal does eat and what it doesn’t.
- Supplements – while most dietary supplements (and there are a gazillion of ‘em) have been shown in independent studies to be pretty useless in managing arthritis, Omega-3 fatty acid supplementation is one of the few things to show some promise in arthritis in dogs. This effect hasn’t been confirmed in other species yet.
- Weight loss – This point should actually be at the top of the list, lit up in fireworks and sequins. Remember how we talked about weight increasing load and deterioration in the joints? Well, when your vet tells you that Fluffy, Fido, Trigger, or Petunia the pot-bellied pig needs to go on a diet to help that limp, take that recommendation seriously. If I could pick one thing as the biggest arthritis helper, it would be weight loss (diet + exercise). My own knees confirm this clinical impression. And, best of all, cutting calories is free!
- Exercise – like diet, exercise is free and extraordinarily helpful in arthritis management. Movement not only helps decrease weight, it promotes circulation, strengthens the muscles and tendons that support the joints, and in some cases improves joint fluid quality. Now, not all joints like all exercises, so check with your veterinarian about the right program for your critter (and with your physician for the right program for you.)
Arthritis can be painful and can decrease athletic performance, but it doesn’t have to be a game-ender. Arthritic animals can have a great quality of life for a long time with decent management. Even if they make more typos in February…
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VIN News Service commentaries are opinion pieces presenting insights, personal experiences and/or perspectives on topical issues by members of the veterinary community. To submit a commentary for consideration, email email@example.com.