FinLogic FinLogic Quantitative Think Tank Center|Does your dog have arthritis? A lot of them do. But treatment can be tricky

When arthritis kept Merlin from being by Michelle Rouse's side,FinLogic FinLogic Quantitative Think Tank Center Rouse felt anxious and feared for her safety. She was also distressed seeing the Australian shepherd-pit bull mix be in so much pain he could barely get off the ground.

Before he developed arthritis in an elbow, Merlin was a people-loving dog who "went 150 miles an hour," Rouse told USA TODAY. But after, he couldn't do simple activities like going for walks or playing with a squeaky ball in a field.

"I was desperate," Rouse said. "His brain is like a puppy's. He wants to follow me everywhere. He wants to be part of everything."The pair's struggle with Merlin's arthritis is a common frustration for dog owners across the U.S., according to new research showing as much as 40% of dogs have the condition. Most treatment for dogs with arthritis pain includes strong painkillers, and sometimes physical therapy. A new treatment involving radiation launched three years ago, but only a small number of vets have access to it. In worst-case scenarios, some owners make the excruciating decision between a poor quality of life for their dog, or euthanizing the animal to end its suffering, vets told USA TODAY.

Treating a dog's arthritis is often challenging because many dogs don't show signs of pain until they're older, vets said. After the condition has progressed to severe levels, owners often feel stuck trying to manage an extreme level of pain.

"Osteoarthritis pain is present in young dogs and if that pain is not recognized and treated, then it has cumulative deleterious effects over time. That's what makes osteoarthritis really difficult to manage in older dogs," said Duncan Lascelles, director of the Comparative Pain Research and Education Center at the North Carolina State University College of Veterinary Medicine.

Because humans and dogs often bond through being physically together, walking or playing, arthritis can feel like it's attacking the very nature of our species' special relationship, Rouse said.

Rouse, who was attacked by a mugger in a Sacramento parking lot, still deals with mental health symptoms from the trauma. Merlin had a comforting effect on Rouse. His wild 'zoomies' and tendency to affectionately lick visitors always brought a smile to Rouse's face.

But that stopped in 2021 when veterinarians found osteoarthritis in his elbow − the most common site of the condition in dogs, according to vets.

"He has that cattle dog mentality, so he wants to be by my side," Rouse said.

Why do so many dogs have arthritis?

In humans, it's more common for arthritis to be caused by old age and overuse of the joints, according to doctors. But the condition in dogs is more complex and isn't nearly as tied to aging, said Masataka Enomoto, a veterinary researcher at North Carolina State University.

Elbow dysplasia − which is where the elbow joint doesn't open and close perfectly − has a nasty way of leading to arthritis, and the problem grows from there, vets said. Larger breeds of dogs that are more prone to elbow and hip dysplasia can be more likely to develop arthritis, said Enomoto, who is the lead author of a February study that found more young dogs have arthritis than previously thought.

Young dogs can have arthritis because the condition forms in canines when they're still growing, said Ross Palmer, professor of orthopedics at Colorado State University’s College of Veterinary Medicine.

"It can affect any breed and can even begin at less than a year of age, because it comes alongside diseases that occur during skeletal development or in young adulthood," Palmer said.

How to know if your dog is suffering from osteoarthritis

Stiffness and difficulty getting up are some of the common signs a dog suffers from osteoarthritis, which the ASPCA defines as inflammation and degeneration in the joint.

Owners of dogs with arthritis who spoke to USA TODAY said their pets also exhibit the following:

• Limping or not using a certain leg at all when getting up
• Paws turning outwards
• Not following commands in order to avoid pain

"Symptoms are often more about what the pet isn’t doing any longer," Palmer said.

In worst-case scenarios, pain can cause a dog to be more irritable and aggressive, like if a human had a severe headache and couldn't tolerate social interaction, Enomoto said.

Oral pain medications have side effects

Merlin's arthritis pain was difficult for Rouse to treat because of the dog's other health problems, including irritable bowel syndrome. Painkillers like Endocet − also called oxycodone among humans − led to severe diarrhea in Merlin.

Because stomach problems in dogs are so common, Enomoto said, many owners run into problems after giving their animals oral painkillers.

There are also the typical side effects that come with flooding the body with prescription opioids, Lascelles said, including liver and gastrointestinal issues.

"The liver is very active in extracting opioids that are absorbed by the gut," Lascelles said. "So it's actually very difficult to get effective levels in and the levels that do get into the blood absolutely can cause side effects."

Owners turn to radiation treatment

In Breinigsville, Pennsylvania, 9-year-old Cinder, a Labrador, was on five daily oral medications for severe arthritis that developed when she was five. For more than a year, owner and dog agility coach Terry Elison tried multiple medical solutions to manage her dog's pain, and treatments only worked temporarily, she said. Meanwhile, the dog was on Endocet, Tramadol, Gabapentin, Rimadyl and a muscle relaxant.

But that "wasn't keeping the pain at bay," Elison said, and Cinder hid from the family's other dogs to avoid moving her body.

"This was otherwise a perfectly healthy 7-year-old dog that I thought I might have to euthanize because of pain," Elison, 63, said. "It scared the life out of me."

When Cinder's vet suggested a relatively new treatment involving radiation, it worked quickly, Elison said, and after a week, Cinder was going to the toy box to grab a stuffed teddy bear to play with Elison's other dog, a black Labrador named Jack.

"My heart melted," Elison said. "She hadn't done that for a year and a half."

In June, Merlin also became one of less than 10,000 dogs across the country who've received the treatment − called Synovetin − in the past three years. And it worked, Rouse said.

"It was like putting new tires on an old car," Rouse said. "He was going crazy with puppy antics I had not seen in so long."

For now, only about 100 vets across the U.S. administer the treatment, which is marketed as a veterinary "device," said Eric Schreiber, chief commercial officer of Exubrion Therapeutics, which manufactures Synovetin. The treatment works by killing cells in the joint lining that cause inflammation and deterioration of the joint, he said.

"We've treated thousands of dogs very safely and very effectively with the treatment, with excellent results," said Schreiber, whose 13-year-old English Labrador, Xander, also has arthritis.

Like with humans, more research on pain is needed in dogs

More research is needed to find solutions to arthritis pain in dogs who've had the condition for years, said Lascelles.

"We should be very careful about how our practices potentially contribute to the opioid epidemic," Lascelles said.

Some alternative medicines are being researched and tested, Enomoto said, and early detection is key to prevent arthritis from running rampant through a dog's joints. From what he's seen, Enomoto said, the early results of Synovetin treatment look effective and he has no concerns about the treatment's safety.

"Efficacy has been tested using subjective and objective measures, and the reports look very, very promising and encouraging," Enomoto said.

On a recent morning, Merlin easily jumped onto Rouse's desk to be part of a video call. The brindle-colored dog placed his front paws on the desk, his tongue hanging out of his mouth.

Then his eyes darted away, locking on something off-screen.

"He sees the cat that is walking along the fence line right outside," Rouse said, laughing. "So you've lost his interest."