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CORVALLIS, Ore. - In a single year, Americans spend an estimated $1.3 billion to repair damaged anterior cruciate ligaments in their dogs, but new research suggests that rehabilitation can provide a viable alternative to surgery for treating partial ACL tears, and a regimen of controlled exercise can help prevent more serious injuries.

When a dog completely ruptures its ACL - which in humans is in the knee - surgery is required, according to veterinary surgeon Wendy Baltzer, who directs the Small Animal Rehabilitation Center at Oregon State University's College of Veterinary Medicine. But many canine ACL injuries are more chronic in nature; left untreated, these partial ruptures can lead to lameness.

Surgery can help dogs with partial ACL ruptures, Baltzer said, but may not be necessary.

"As we've started doing rehabilitation on some dogs, and preventive therapy on others, we've found remarkable improvement in the physical conditions of pets that five years ago would have been euthanized," Baltzer said.

"Unfortunately, there's not a lot of research in the journals about rehabilitation for ACL injuries in dogs and much of what we know we've borrowed from studies on humans," she added. "But this new field is showing a great deal of promise and research at Oregon State and elsewhere will lead to further progress."

Baltzer, who is writing a book on the prevention of injuries in dogs through training, said ACL problems are most frequently found in mid-sized and large dogs, and appear more common among dogs that have been spayed or neutered. One theory is that spaying and neutering causes a hormonal imbalance leading to a weakening of the ligaments, but that hypothesis needs to be tested, she emphasized.

ACL injuries also are common among "sports" dogs, or those that compete in agility trials, dock jumping, or Frisbee catching.

Treatment options vary depending on the severity of the injury, the size and breed of dog, and the facilities where the treatment may take place. At OSU's new Canine Rehabilitation Center, which opened in October of 2008, dogs can be worked out on an underwater treadmill, undergo laser therapy, and perform a series of resistance-training exercises using stretchable harnesses.

A treadmill with sensors in Baltzer's lab can identify how much weight a dog is exerting on each leg while walking, and a small disparity in weight distribution can be one indicator of a partially torn ACL or early stage osteoarthritis.

"Dogs don't always tell us when they're in pain," Baltzer said. "They'll run and jump and act goofy because that's what dogs do. But if they're doing that when they have a slight injury - and it's left untreated - it can develop into a more serious, even traumatic injury, and that's what we're trying to prevent."

Surgeries usually run from a minimum of $1,000 to $5,000 or more. Rehabilitation treatment options vary depending on whether the dog has to be boarded, but typically may cost a few hundred dollars instead of several thousand.

Baltzer said she recently treated a three-year-old Springer spaniel - a "beautiful dog," - whose career as a show dog never really took off because of two partially ruptured ACL joints. When the dog was in a show, she said, he moved awkwardly and received commensurate scores.

"After just three weeks of treatment, his pain was resolved and he won the first show he entered," Baltzer said. "You could just see the difference. Five years ago, we would have recommended surgery. Now treatment on the underwater treadmill and some specially designed exercises had him walking like new."

The key to therapy for dogs is similar to the treatment of humans, she pointed out. Exercise the core muscles and make sure the joints are properly aligned before the dog begins to exercise. Like humans, dogs will compensate when a muscle or joint isn't working properly - and that leads to more problems.

Baltzer said there are three keys to preventing ACL injuries in dogs:

• Foremost, don't allow your dog to become overweight. Obesity puts a strain on the joints and leads to an unnatural gait during exercise.

• Insist on providing regular exercise for your dog.

• If you are planning a major outing - a long hike through the woods, or running your dog on a snowy trail through the mountains - prepare them for it by working them gradually into shape.

"You wouldn't run a marathon without preparation," Baltzer said, "but your dog will do it because they're so excited."

Though it only opened a few months ago, the Small Animal Rehabilitation Center at OSU treats five to 10 cases a week - a combination of referrals from veterinarians and pet owners who are seeking options to surgery. The center was funded through $130,000 in private donations and serves as a research laboratory as well as a treatment facility.

Baltzer and her colleagues have begun a number of research projects trying to fill the literature gap and are looking at oxidative stress in agility dogs, and different protocols for post-surgery rehabilitation.

The OSU center also treats cats, especially those with osteoarthritis, an affliction that affects some 80 percent of cats over the age of 13.

More information on the center is available at: http://oregonstate.edu/vetmed/hospital/clinical/sa-rehab, or pet owners can call 541-737-4812.

For a video to illustrate the following story: http://oregonstate.edu/media/cbsdrf