New genetic test identifies dogs’ risk of cruciate ligament rupture

Cruciate ligament ruptures are one of the biggest problems in canine orthopedics, but there is now a way to help prevent this disabling disease through genetic testing.

Researchers in the Comparative Genetics and Orthopaedic Research Laboratory at the University of Wisconsin-Madison School of Veterinary Medicine have found a way to determine whether a dog is susceptible to the condition. The screening test, one of the first genetic tests for a common complex disease in dogs, requires only a cheek swab that can be collected at home or a small blood sample.

The researchers made the screening test available in September for Labrador Retrievers, the most popular dog breed in the United States. About 5% to 10% of Labrador Retrievers will rupture a cruciate ligament within their lifetime, according to information from the laboratory.

The research team is now working to extend the development of predictive genetic testing to other breeds with a high risk of cruciate rupture, such as Rottweilers and Newfoundlands.

“In dogs, ligament degeneration and progressive rupture of collagen fibers in the ligament tissue leads to the development of knee joint instability over time,” said Dr. Peter Muir, laboratory co-director and a professor in the Department of Surgical Sciences at the UW School of Veterinary Medicine.

Both genetic factors and other characteristics, such as physical health, body condition, and neutering, contribute to chronic ligament degeneration. Determining whether a dog is more likely to rupture a cruciate ligament because of genetic factors allows the dog’s owner and veterinarian to take preventive measures, such as keeping the dog at a healthy weight and monitoring for signs of emerging injury.

Dr. Muir explained that the genetic markers for cruciate ligament ruptures are more complex than markers for other traits. Most genetic tests look for a specific DNA mutation to determine whether a particular disease or trait is present. However, the predilection for cruciate ligament rupture results from multiple gene variations throughout the dog’s genome.

The researchers used a method called array genotyping to determine genetic markers for more than 1,000 Labrador Retrievers. By analyzing the DNA and gene variants in multiple samples, the team could identify the small variants associated with cruciate ligament rupture.

The researchers found that for each individual Labrador Retriever that ruptures a cruciate ligament, about 62% of the risk is genetic. Based on the reference population, the predictive testing has an accuracy of about 98% for predicting whether Labrador Retrievers will rupture a cruciate ligament.

The new test not only can allow pet owners to take steps to prevent this disabling disease but also can help breeders reduce the incidence of the condition in Labrador Retrievers over time to improve the breed’s genetic health. Testing costs $250 and takes four to six weeks for results. More information is available by contacting the Comparative Genetics and Orthopaedic Laboratory at geneticsvetmed [dot] wisc [dot] edu.