Understanding Osteoarthritis in Pets: What It Is, How It Starts, and Why Dogs, Cats, and Rabbits Experience Joint Pain So Differently
By Dan Gray, DVM • Gentle Vet, Green Bay, WI
Here's a number that surprises most people. When researchers at North Carolina State University X-rayed every joint of 123 ordinary young dogs, all between 8 months and 4 years old, about 4 in 10 already had arthritis changes in at least one joint (Enomoto et al., 2024). Most of their owners had no idea.
Osteoarthritis isn't only an old-dog problem, and it isn't only a dog problem. Cats get arthritis. So do rabbits. As Dr. Dan Gray puts it, arthritis can happen in "any animal with bones and joints." What changes from species to species is how the disease starts, and how well your pet hides the pain.
What Is Osteoarthritis, Exactly?
Osteoarthritis, also called degenerative joint disease or DJD, is the most common type of arthritis in pets. Most people think they already know what osteoarthritis is: stiff, old joints. Knowing what actually happens inside the joint explains why treatment works. Osteoarthritis is also a big deal: the American Animal Hospital Association calls osteoarthritis the most common form of chronic pain in dogs (AAHA, 2022).
A healthy joint has two built-in protections. Cartilage covers the ends of the bones and acts as padding. Joint fluid acts as lubrication. Dr. Gray explains that osteoarthritis usually develops down one of two paths.
Path one: the body tries to "fix" an unstable joint
When a joint is loose or unstable, whether from a torn ligament or a joint that didn't form correctly, the body tries to reinforce the joint by thickening the surrounding tissue and adding new bone.
“At best case, that process is limiting on motion. At worst case, some of that process is painful, so every step becomes painful.”
— Dr. Dan Gray
Path two: the padding and lubrication wear away
Other times, the cartilage itself breaks down. Right after an injury, a joint often swells with extra fluid. In later-stage arthritis, the opposite happens: the cells lining the joint produce less fluid, and that fluid lacks the lubricating building blocks (glycosaminoglycans, or GAGs) that keep the joint comfortable. Less lubrication means faster wear, and what's underneath the cartilage was never designed to take impact.
“When the cartilage is destroyed, that allows areas that have a lot of nerves to become exposed and irritated. And that's where the pain comes from.”
— Dr. Dan Gray
Either way, the joint's shape and function change, and the reshaped joint keeps the damage cycle going.
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The bottom line on osteoarthritis Osteoarthritis can't be cured, but the disease is usually manageable. Treatment doesn't rebuild the joint. Treatment controls pain, protects function, and slows the cycle of joint destruction, and works best when started early. |
Where Does Osteoarthritis Come From?
"As always, the source is complex," Dr. Gray says. Most cases trace back to some combination of genetics, injury, age, and body weight.
Genetics: hip and elbow dysplasia
Hip and elbow dysplasia are inherited, and some breeds are far more prone to these conditions. Breeders can screen parent dogs, and screening X-rays in young dogs can estimate a pet's risk. But screening isn't perfect and rarely changes treatment at that stage. Most of us own the puppy, not the parents, so genetics is the part we control least.
The "happy dog injury": cruciate ligament tears
The cranial cruciate ligament (CCL) is the dog version of the human ACL, and a tear is one of the most common routes to arthritis in a dog's knee.
“I often refer to a CCL tear as a happy dog injury. The dog is out living their best life, makes a sharp right turn, and the ligament pops. A CCL tear is very similar to someone playing basketball who lands wrong and tears their ACL.”
— Dr. Dan Gray
There's a genetic side to CCL tears, too. Dr. Gray learned knee surgery from Dr. Vicki Wilke, whose research at Iowa State University helped show that cruciate ligament rupture is inherited in Newfoundlands (Wilke et al., 2006). Closer to home, researchers at the University of Wisconsin–Madison School of Veterinary Medicine estimate that about 62% of a Labrador Retriever's risk of CCL rupture is genetic (AVMA News, 2022). A torn ligament leaves an unstable knee, which puts the knee squarely on path one.
Age: the quiet cause in cats and rabbits
Age plays a role in dogs, but age is a much bigger driver in cats and rabbits, and that's why arthritis in these species gets overlooked. Quiet indoor pets don't seem to do anything hard on their joints, so owners conclude the problem can't be arthritis. But simple aging is enough to damage a joint. In cats, arthritis shows up most often in the spine, hips, knees, and elbows. Rabbits are especially prone to arthritis of the spine.
How common is joint disease in cats? When researchers X-rayed the joints and spines of 100 randomly selected cats, 92% had evidence of degenerative joint disease, including young cats (Lascelles et al., 2010). And in rabbits, a University of California–Davis study found naturally occurring osteoarthritis was strongly linked to both age and body weight (Arzi et al., 2012).
Body weight: the part you can control
Extra weight means extra force on every sore joint, every step of the day. In a landmark lifetime study of Labrador Retrievers, dogs fed 25% fewer calories than their littermates lived a median of 1.8 years longer and developed late-life diseases, osteoarthritis especially, later (Lawler et al., 2008).
“The longer you keep your pet lean, the less impact your pet will feel from arthritis. It's very difficult to get an overweight animal to lose weight later in life. It's significantly easier to keep a properly weighted animal lean as they get older. So please start young.”
— Dr. Dan Gray
Why Does Osteoarthritis Look So Different in Dogs, Cats, and Rabbits?
Osteoarthritis is the same disease with three very different presentations. We've written before about how pets show pain in general [https://www.thegentlevets.com/services/blog/15-ways-cats-and-dogs-tell-us-theyre-pain]. Here's what's specific to osteoarthritis in each species.
Dogs: the most visible, and still often missed
Dogs show the most outward change: stiffness after naps, shorter walks, hesitation at stairs or the car, back legs sliding out on a smooth floor. Even so, in that NC State study, owners had noticed a problem in only about 30% of young dogs with painful arthritis, and just two of those dogs were being treated (Enomoto et al., 2024).
Cats: read the hair coat
Cats are masters at hiding pain. Arthritis in cats can slip past even a veterinarian in the exam room. One of the best clues is grooming. In a cat who is not overweight, watch for mats along the back, over the base of the tail, or around the rear end, dirty paws, or litter stuck in the claws of the back feet. In a lean cat, poor grooming usually means the spine is too sore to bend and groom.
When an owner isn't convinced, Dr. Gray often recommends a treatment trial as a diagnostic step. Once bloodwork confirms a cat is healthy enough, a few weeks on a pain reliever (a monthly Solensia injection or an oral pain medication) can answer the question. If the cat starts grooming and jumping again, that improvement is the proof. Learn more about our cat care.
Rabbits: "He's not old. He's hurting."
Rabbits may be the most overlooked arthritis patients of all, and rabbit arthritis is usually found on exam rather than at home. The clues are a urine-stained or messy rear end, unkempt feet or sores on the bottoms of the feet, uneaten cecotropes (the soft, nutrient-rich droppings rabbits normally eat straight from their bottom), and a general drop in activity. Nearly always, owners chalk these changes up to age.
“Most clients just don't connect yet that arthritis can happen in any animal with bones and joints. It can be very difficult to get owners to trust us that yes, your rabbit's not old, it's actually in pain.”
— Dr. Dan Gray
Arthritis pain affects the gut, too. Pain slows a rabbit's digestive tract, and chronic arthritis pain is one recognized contributor to recurring GI stasis, now often called rabbit gastrointestinal syndrome (RGIS) (University of Minnesota, Bunny Bellies). Gentle Vet sees rabbits and other small mammals as a regular part of our exotic animal medicine service.
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From our exam room: a 9-year-old rabbit Dr. Hofmann saw an older rabbit who had nearly stopped moving and grooming. Matted fur and trapped urine and feces had caused a large, infected wound on his inner thigh. Once the wound healed, treating his arthritis gave him enough comfort to groom a little, and, more importantly, to tolerate his owner's help, which kept the sore from returning. "While the rabbit is not in perfect condition," Dr. Gray says, "it is a vastly improved life": no open sore, no urine or fecal scald, and his arthritis pain partly controlled. |
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⚠ When a rabbit needs to be seen today A rabbit who stops eating or stops passing droppings is an emergency, not a wait-and-see problem. Call us right away, or see our emergency care page for guidance. |
How Do Veterinarians Diagnose Osteoarthritis?
Diagnosis starts with you, because what your pet has stopped doing is often the most important clue. Then comes a hands-on exam for thickened joints, reduced range of motion, pain responses, and muscle loss over the back legs.
X-rays (radiographs) confirm the diagnosis, pinpoint the joints involved, help decide whether surgery is reasonable, and in rabbits can explain recurring GI stasis. In Dr. Gray's view, the most important job of an X-ray is ruling out something worse.
“A swollen, painful joint can be advanced arthritis. It can also be something more sinister, like a bone or joint tumor. We don't want to miss that.”
— Dr. Dan Gray
Because osteoarthritis is incurable but manageable, we don't repeat X-rays just to watch the disease progress unless there's a compelling reason. Learn more about our in-house diagnostic services.
What Helps Arthritis Most? (Hint: The Answer Isn't a Pill)
We've covered arthritis treatment options for dogs and cats [https://www.thegentlevets.com/services/blog/your-pet-slowing-down-it-might-not-be-just-age] before, so here's just the one thing Dr. Gray wants every owner to hear:
“There is nothing more effective for pain control than having less weight on a painful joint. It is the most healthy, it is the cheapest, it has the fewest side effects, and it is way more effective than any drug or treatment any veterinarian has.”
— Dr. Dan Gray
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⚠ Weight loss should be steady, not fast Crash diets are dangerous for pets. Cats that lose weight too quickly can develop a serious liver condition (hepatic lipidosis), and rabbits can slip into GI stasis. Make weight loss the first priority, but lose the weight on a vet-guided plan at a safe pace. |
Beyond weight, small changes add up: non-slip rugs on slick floors, ramps for stairs, furniture, and the car, low-sided litter boxes for cats and rabbits, and your help with grooming when your pet can't reach.
In the clinic, one option that often gets forgotten is therapeutic laser, a drug-free treatment that can be very helpful for some arthritic pets. Some clients also report excellent results with chiropractic care and acupuncture. Gentle Vet doesn't offer chiropractic or acupuncture services, but we're happy to work alongside and refer you to veterinarians who do.
Frequently Asked Questions About Osteoarthritis in Pets
Is osteoarthritis the same thing as arthritis?
Osteoarthritis is the most common type of arthritis in dogs, cats, and rabbits. Osteoarthritis is also called degenerative joint disease (DJD). Osteoarthritis develops when a joint becomes unstable or its cartilage and joint fluid break down, leading to inflammation, extra bone growth, and pain.
Can indoor cats and house rabbits get arthritis?
Yes. In cats and rabbits, age alone is a major cause of osteoarthritis, even in quiet indoor pets. One study found X-ray evidence of joint disease in 92% of randomly selected cats. Rabbits are especially prone to arthritis of the spine.
What are the signs of arthritis in a rabbit?
Rabbits rarely limp. Look for a urine-stained or dirty rear end, unkempt or sore feet, uneaten cecotropes (soft night droppings), and less hopping. These signs are often mistaken for normal aging.
Can osteoarthritis in pets be cured?
No, but osteoarthritis is usually manageable. Weight control, home changes like non-slip flooring and ramps, pain medication, and therapies such as therapeutic laser can keep pets comfortable and active for years.
What is the single most effective thing I can do for my pet's arthritis?
If your pet is overweight, help your pet reach a healthy weight on a gradual, vet-guided plan. Less weight on a painful joint is the most effective, least expensive, and safest form of arthritis pain control there is.
Is It "Just Age," or Is It Arthritis? Let's Find Out Together
If your dog has slowed down, your cat has stopped grooming her back, or your rabbit's rear end never seems clean anymore, those changes are worth a closer look. Schedule a mobility and arthritis exam with our team. We see dogs, cats, rabbits, and many other exotic pets, and our Low Stress Silver Certified approach keeps visits as calm as possible.
Helpful tip: Bring a short phone video of your pet getting up, walking, using the stairs, or using the litter box at home. Pets often act very differently in the exam room.
Gentle Vet Animal Hospital
2560 University Ave, Green Bay, WI
(920) 435-5000
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