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A dog gets a chiropractic assessment at the Tufts University School of Veterinary Medicine.
One morning last August, Mary Arabe’s 9-year-old gray and black tiger cat, Leo, came home from a night out exploring with a severe limp and an elbow swollen three times its normal size. He was clearly in pain; Ms. Arabe thought he had dislocated his shoulder during a fall.

“He kind of lay around the barn that day; you could tell he was hurting,” said Ms. Arabe, who lives on a 25-acre farm in Rogers, Ohio, with 10 chickens, three horses, three cats and two dogs. “He was in so much agony I thought, ‘If someone can’t remove this animal’s pain I have to put him down.’”

She took Leo to the veterinarian, who said he could do nothing for him. Despondent, she took him to Rick Tsai, a chiropractor in Darlington, Pa., who a few years earlier had adjusted Ms. Arabe’s puggle, Bustar, after a head and neck injury.

An X-ray found no broken bones, but there was a large amount of swelling and fluid retention. Dr. Tsai couldn’t make any promises, but he placed his hands on the cat’s spine, hips and neck and manipulated the joints until they popped.

“We brought the cat home, and the next day he was walking fine,” said Ms. Arabe. “Two thirds of the swelling in the arm was gone. Whatever Dr. Tsai adjusted, it worked. He healed him.”

Millions of people swear by their chiropractors, and chiropractic has long been a mainstay in the equine world, especially among show or racehorses. Now it is gaining popularity among pet owners, as a way to treat household pets suffering from arthritis, sprains, joint pain and other ailments.

Animal, or veterinary, chiropractic originated around 1895, when human chiropractic first began. But it did not gain wider appeal until 1987, when the late Sharon Willoughby-Blake, a veterinarian and chiropractor, started Options for Animals in Hillsdale, Ill., which taught vets and chiropractors how to adjust animals. Two years later, the American Veterinary Chiropractic Association, a professional membership group and the main certifying agency in North America, was formed.

According to Robbie Hroza, vice president of operations for Options for Animals, about 2,000 students have gone through their program. Over the last two years, student enrollment has increased by 50 percent; a good portion are recent graduates of veterinary or chiropractic schools, she said.

Still, the practice remains controversial, in both people and pets. While some studies have found that chiropractic care can be more effective than medications for people with problems like neck pain, others have linkedforceful neck manipulation to strokes. Other researchers have found that unfavorable chiropractic outcomes are under-reported in medical trials.

There are only a few scientific studies about chiropractic’s efficacy on animals, and tensions exist both within and between the chiropractic and veterinary communities. The American Holistic Veterinary Medical Association, a trade organization, reports that in 2012 about 900 of the estimated 97,000 veterinarians in the United States practiced some type of animal adjustment.

In some states a chiropractor is not allowed to touch an animal without either a veterinarian’s referral or direct veterinary supervision. And in itspain management guidelines for dogs and cats, the American Animal Hospital Association and the American Association of Feline Practitioners caution, “chiropractic methods potentially can cause injury through the use of inappropriate technique or excessive force.”

“There is currently insufficient published evidence of efficacy in dogs and cats to make specific recommendations about the use of chiropractic intervention,” they add.

Indeed, since 1994, the American Chiropractic Association’s position has been that the term “veterinary chiropractic” is a misnomer and should “not be used to refer to the application of manipulative techniques to animals.”

To get around it, many veterinary practitioners use other monikers, at least for official purposes. At The Healing Oasis Wellness Center in Sturtevant, Wis., students are trained in “veterinary spinal manipulative therapy”; enrollment has tripled since opening in 1993, according to co-owner Michelle Rivera.

The American Veterinary Chiropractic Association calls the 1,000 plus vets and chiropractors that have gone through its training “AVCA certified doctors.”

Dr. William L. Inman, a veterinary surgeon and head of the International Association of Veterinary Chiropractitioners (also known as the American Animal Adjusting Association) in Coeur D’Alene, Idaho, offers “veterinary orthopedic manipulation,” or VOM, which involves applying a six-inch long, stainless steel, rubber-tipped Activator-like device on an animal’s spinal column. The 8,300 people who have gone though his course earn the title of “certified veterinary chiropractitioner.”

Many chiropractors think the rules are unfair to pet owners. “A person should be allowed to take their animal anywhere they want if they think it benefits them,” said Dr. Tsai, the chiropractor who treated Ms. Arabe’s cat. He has worked in tandem with veterinarians over the years, but acknowledges that many of them don’t like his field because it takes business away from them.

“Do you really think that a few weeks course can possibly teach a vet the skills that has taken a good chiropractor years to learn?” said Dr. Tsai, who has adjusted everything from raccoons to owls out of his home office in East Palestine, Ohio.

Gene Giggleman, a veterinarian, animal chiropractor and a professor of anatomy at Parker University College of Chiropractic, in Dallas, which has trained more than 400 vets and chiropractors in animal chiropractic, thinks it’s more about a lack of knowledge. “My philosophy as a vet is ‘chiropractic first, drugs and surgery second,’ but a lot of vets don’t understand or know about animal chiropractic, and so they don’t refer people,” he said.

Other veterinarians say their reservations are more about the health of the animal.

Dave Geiger, a veterinary neurologist near Santa Fe, believes that animal chiropractic has the potential to be harmful because “it’s performed by practitioners who often have very little background knowledge of veterinary neurology — or veterinary medicine at all — and thus are unable to fairly evaluate the theoretical or actual effects of their practices.”

“Some practitioners even promote veterinary chiropractic for conditions that it is potentially dangerous for, like degenerative disc disease,” he added. “It should be clearly identified as an unproven therapy, and practitioners should be prevented from making claims about its effects.”

Still, as with most kinds of alternative therapy, adherents often can’t be swayed.

“If it’s good enough for us, why not them?” said Dee Hayes, a yoga instructor in San Diego who shared the same chiropractor with her cocker spaniel, Charlie, for six years.

Patricia Kallenbach, a holistic veterinarian in Crystal River, Fla., said the field is growing because the client base demands it. “They’re saying, ‘If I’m going to eat better, I’m going to get my pet to eat better,’” she said. “‘If I can benefit from chiropractic care on my body, so can my pet.’”

Chiropractic also tends to be much cheaper than veterinary care, with visits costing as little as $35, depending on the type of animal and, of course, the practitioner.

To that end, learning another modality is beneficial to veterinarians, many of whom have been struggling financially. “It’s a practice builder in that you can offer another service without a huge amount of training,” said Dr. Kallenbach, who recently added chiropractic, massage therapy and acupuncture to her practice (in addition to massage for humans).

Maureen Wilkins and her 6-year-old Russian Peterbald cat, Isak, both get adjustments from Shannon Gaertner-Ewing, a chiropractor in Nampa, Idaho. Ms. Wilkins, 60, had been seeing Dr. Gaertner-Ewing herself on a weekly basis and started bringing in Isak three years ago.

“Isak is inclined to get grumpy, and it’s my understanding that’s usually because he’s hurting,” said Ms. Wilkins, a retired teacher who pays $20 per visit. “So, when Isak gets particularly grumpy and starts beating up on his feline brother or he jumps someplace and then falls off, we take him to Dr. G. She adjusts him, and it’s like Dr. Jekyll and Mr. Hyde. His attitude improves, he becomes Mr. Cuddles. He can’t get enough affection.”

Ms. Wilkins maintains that Isak can sense in advance when it’s time to visit Dr. Gaertner-Ewing. “When I put down the car carrier he’ll leap into it,” she said. “He is thrilled to go. As soon as he sees her, he’s practically drooling.”