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Tearing or rupturing of the anterior cruciate ligament (ACL) is one of the most common causes of limping in dogs. In the vet world, the ACL is also known as the CrCL or cranial cruciate ligament. This is a ligament in the knee joint that runs between the thigh bone and shin bone and is responsible for stabilizing the knee.
Dogs are very prone to ACL rupture due to their anatomy and gait, as well as other factors such as obesity, which is surprisingly common in the canine population. When you read about ACL injuries in dogs, surgical repair is often recommended. But is it necessary? And what if your dog—due to their age or other health problems—is not a good candidate for surgery?
Many dogs do quite well without surgical repair of their torn ACL, though this is dependent on several factors. Other dogs end up needing surgery, even with excellent non-surgical rehab plans.
Where is the ACL in Dogs Located?
The ACL or CrCl is a small band of tough fibrous tissue that runs from the back of the thigh bone (femur) to the front of the shin bone (tibia). Its job is to prevent the shin bone from sliding forward in relation to the thigh bone. It is also responsible for preventing over-extension of the knee.
Why Does the ACL Tear in Dogs?
When it comes to tearing or rupturing the ACL, dogs are very different from humans. In people, a ruptured ACL usually occurs during some form of sporting activity or exercise, as a traumatic injury. In dogs, the process is much slower. The ACL is gradually worn down over time, as strands of the ligamentous tissue weaken; this process has been likened to the fraying of a rope. Eventually, the ligament will rupture, and the knee joint loses its stability.
The bottom line is this: we don’t exactly know why ACL tears are so common in dogs. The condition is multifactorial, meaning a number of factors contribute to the outcome. Certainly, large breeds of dogs seem more prone to ACL rupture than small or toy breeds. Some breeds, such as Labradors, Rottweilers, and Boxers, appear to be particularly prone.
Other factors such as obesity and conformation of the bones in the joint often play a role. And, lastly, factors such as early de-sexing, inflammatory conditions, and activity may or may not be important.
What Happens When the ACL is Torn?
Several things happen when a dog’s ACL is torn. Limping is the most common sign owners will notice. This may be acute if the ligament ruptures after months or years of “fraying”. However, the limp may also be slower in onset, developing over time, or maybe even “coming and going”. The limp varies in severity—some dogs will have a slight limp, while other dogs will be reluctant to bear any weight on the affected leg.
Inside the joint, the body responds to the ruptured ACL by sending inflammatory cells there to initiate healing. This results in pain, and, ultimately, arthritis. It is important to mention that since the rupturing of the ACL is a slow process in dogs, caused by the accumulation of many “micro traumas”, arthritis is usually already present by the time the ACL tear occurs.
Lastly, without an intact ACL, the thigh bone is allowed to slide backward, pushing the shinbone out in front.
Non-Surgical Management of Torn ACLs
When Is It Appropriate?
In our opinion, there are four main instances in which non-surgical management of ACLs is appropriate.
Does It Work?
Does non-surgical management of torn ACLs actually work? The answer to this question is not a clear-cut “yes” or “no”.
What Does It Involve?
Management of ACL ruptures without surgery is still quite an intensive process, requiring your commitment as an owner. It is multifaceted, and aims at restoring joint health in a number of ways:
Surgical Management of Torn ACLs
Surgical repair has, for some time, been the cornerstone of torn ACL management in dogs. Surgery is, of course, much more invasive than non-surgical approaches. There are a number of techniques to choose from; this decision is dependent on a dog’s breed, a surgeon’s capabilities, and an owner’s financial limitations.
In general, all surgeries carry an excellent prognosis for the return of normal function to the leg.
When Is It Appropriate?
There are several instances in which surgery may be a better option than non-surgical management:
Does It Work?
Surgery has a very high success rate for the return of function to the limb. The best of the surgical options, known as a TPLO, is successful 90–95% of the time. As with any surgery, complications are possible. These include infection, implant failure, bleeding, swelling, and anesthetic complications.
What Does It Involve?
As we mentioned, there are a number of different surgical options for repairing torn ACLs in dogs. A full discussion of surgical options is beyond the scope of this article, but surgeries are broadly categorized as either “extracapsular” or “intracapsular”. Extra-capsular surgeries such as the De-Angelis suture or Tightrope involve placing a synthetic material around and through the bones of the knee joint, essentially mimicking the function of the ruptured ligament.
Intracapsular repairs, such as the gold-standard TPLO (tibial plateau leveling osteotomy), involve cutting bones and realigning the slope of the shin bone, thus stabilizing the knee joint. With all surgeries, a period of crate rest and then restricted exercise is essential; this may be necessary for 2–3 months.
Conclusion
Torn ACLs are common in dogs and can leave dog owners in a tricky predicament. At this stage, surgery carries a better prognosis for large dogs. In small dogs, both surgical and non-surgical options lead to good outcomes. Choosing the right path is dependent on your values, your budget, and your ability to commit to the recovery phase, as well as your dog’s age, breed, and temperament.
Whatever you choose, ensuring your dog is comfortable and pain-free should be the top priority. If your dog is limping or has been diagnosed with a torn ACL, always start by arranging a prompt consultation with a veterinarian. Early intervention and action will lead to the best outcome for you and your dog.
Featured Image Credit: Yekatseryna Netuk, Shutterstock
