Device may help keep dog knees limber

As our canine companions get older, a common joint problem could leave many of them stiff in the knee. Fortunately, a new device developed by researchers at UW–Madison’s School of Veterinary Medicine (SVM) may help veterinarians catch the problem early – before it results in permanent arthritis.

As dogs age – particularly larger breeds, like golden or Labrador retrievers – the cranial cruciate ligament in the knee may weaken and stretch. After it reaches a certain point, the ligament ruptures.

“The minute this happens, arthritis sets in,” leaving the dog stiff and often in pain, says Mandi Lopez, a veterinary surgeon, SVM researcher and co-inventor of the device. Surgeries to repair a ruptured ligament, which can never fully be restored, are the most common procedures performed on dogs today, adds Lopez.

The ideal course of action is to detect weakened ligaments before they rupture. Early detection, says Lopez, could lead to preemptive surgeries that restore the function of the ligament before it’s destroyed and unable to be completely repaired.

But current detection methods cannot discern partial disruptions. Right now, veterinarians rely on physical exams to reveal knee-related problems. In the case of the cruciate ligament, just a few millimeters of movement in a leg bone can signal a partial disruption.

“It is very difficult to detect such minute motion using our hands,” says Lopez.

Needing a tool that could objectively assess knee stability after cruciate ligament repair surgery, Lopez, along with veterinary surgeon Mark Markel and instrument specialist William Hagquist, developed a device that can detect motion within the joint down to just one-tenth of a millimeter.

“Since we’re one of the leading cruciate research groups in the country,” says Markel, “having something to quantify ligament disruption will make our research more robust.”

The new device consists of a platform with two moving pieces. One piece is strapped to the dog’s leg just above the knee and the other is strapped just below it. As a small force is applied to the lower piece, pushing it backward or forward, X-rays of the joint are taken. The images, along with one taken when no force is applied, are superimposed to show the amount of movement in the joint. By looking at the measurements, veterinarians can distinguish between intact, partially disrupted and fully ruptured cruciate ligaments.

“I know how devastating a ruptured cruciate can be,” says Lopez. “The device has tremendous potential to improve the quality of life of our pets by allowing us to diagnose problems early and intervene before arthritis develops.” She adds, “If I could prevent a cranial cruciate rupture in my own dogs, I would.”

The inventors are currently designing clinical trials using the instrument, which is patented by the Wisconsin Alumni Research Foundation, a non-profit agency that manages intellectual property for UW–Madison.

Because many species, including humans, can suffer from ruptured cruciate ligaments, the inventors say the device could be adapted for use on other animals or incorporated into other imaging technology. They note, however, that similar detection tools already exist for people.