Researchers at Cornell University have uncovered compelling evidence that dogs may be vital allies in understanding and treating one of the most common and debilitating sports injuries in humans: anterior cruciate ligament (ACL) tears.

A recent study published in the Journal of Orthopedic Research highlights a surprising biological link between dogs and humans when it comes to ACL injuries and the development of post-traumatic osteoarthritis (PTOA), a painful and often chronic condition that can follow ligament damage. The discovery centers on a protein called periostin, which was found to be highly elevated in the joint fluid of both species after an ACL injury.

“Dogs naturally develop ACL injuries and PTOA much like humans do,” said Sydney Womack, the study’s lead author and a dual Doctor of Veterinary Medicine (DVM) and Ph.D. candidate at Cornell’s College of Veterinary Medicine. “Our study supports the idea that we can learn more about human medicine by studying disease progression in dogs.”

ACL tears are particularly common among young athletes—especially females—and while current treatments like surgery can restore some function, they often fail to prevent long-term joint damage. Scientists still don’t fully understand why some individuals develop osteoarthritis sooner or more severely than others.

To explore this, researchers at Cornell and the Hospital for Special Surgery (HSS) in New York City analyzed joint fluid from both canine and human patients. Their findings were striking: around 60 per cent of the proteins in the samples overlapped, and periostin was the most prominently upregulated protein in both groups. Previously, periostin had been documented in humans with ACL injuries but not in dogs.

“This overlap is exciting,” said Dr. Heidi Reesink, senior author and associate professor of clinical sciences at Cornell. “It suggests dogs could serve as a powerful model for understanding the mechanisms behind PTOA and testing new treatments.”

One key advantage of using dogs in this research is their shorter lifespan, which allows scientists to observe disease progression and potential therapeutic effects much more quickly than in humans. Access to joint fluid samples from dogs is also easier, making longitudinal studies more feasible.

Womack is now focusing on how periostin may influence disease development and whether it could serve as a therapeutic target or early biomarker of osteoarthritis risk.

“Periostin might play a helpful role in early wound healing, but when its expression stays high, it could drive harmful inflammation and joint damage,” she explained.