Dogs who compete in agility and flyball and lack core strength have a higher rate of cranial cruciate ligament rupture which is similar to ACL in people.
According to Dr. Deb Sellon, a Washington State University veterinarian, some types of exercises and the size and shape of the dog increase the risk of knee damage. The exercises that increased the risk were short walks, runs over hilly or flat terrain, even if done on a weekly basis. The exercises that seem to help build core strength are balance exercises, and wobble boards. Dogs that competed frequently in agility at a higher level (more technically rigorous courses) built more core strength.
Regular exercise such as swimming, playing fetch or frisbee, walking or running didn’t increase or decrease the risk of injury.
It seems that Labrador Retrievers, Rottweilers and Australian Cattle dogs were high risk breeds. The researchers also felt that having or not having a tail could be a factor.