In dogs, the cruciate ligament tends to undergo degenerative changes that weaken it prior to rupturing. This very different from ACL injuries in people, where rupture is often associated with a traumatic injury as a result of an accident or incident while taking part in activities like skiing or playing football. While the human ACL and canine CCL are analogous with regard to function, this fundamental difference in onset of injury helps to explain why treatment options in dogs are quite different to those in people.
The mechanism for cruciate ligament degeneration prior to rupturing is not clearly understood, but it is clear that certain factors predispose certain dogs to sustaining a cranial cruciate ligament injury. Certain breeds, such as Labradors and Rottweilers (and other large breed dogs), are much more commonly affected than others, as well as dogs that are overweight. This suggests there is an inherited component to the condition, possibly related to conformation or gait and/or the displacement of weight within the stifle (knee) joint. While there is nothing that can be done to prevent CCL injury, by recognizing the symptoms of CCL damage soon after onset you can give your dog a head start with recovery.