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Torn ACL in Dogs

Canine ACL/CCL Injuries

By far the most common orthopedic injury in all of veterinary medicine is ACL tears in dogs. In human medicine, ACL stands for Anterior Cruciate Ligament. In veterinary medicine that same ligament is commonly referred to as the CCL (Cranial Cruciate Ligament). For the ease of explanation we will be using ACL.

ACL Tears in Dogs are common but very treatable

Since cruciate ligament injury in dogs is the most common orthopedic injury in dogs, there has been a tremendous amount of research around what is the best way to fix the problem. But before we ever discuss ways to fix the problem it is imperative that the injury itself is properly diagnosed. Although there are a variety of ways to diagnose ACL injuries in dogs, the benchmark that most veterinarians use to make this diagnosis is based upon these criteria:

  • The owner's description of the injury
  • The clinical evaluation during active walking and sitting
  • Palpating or "feeling" the joint for swelling or heat
  • Evaluating Cranial Drawer signs
  • Evaluating Tibial Thrust Signs
In order to properly evaluate, your veterinarian may ask permission to lightly sedate your dog with anesthetics in order to have your dog relax properly. Often times, the dogs are under stress from the pain and from simply being at the veterinary office that they tense up their muscles surrounding the knee and therefore it makes near impossible to properly evaluate knee joint and ligament injuries. Sedation is key!

Evaluating Dog ACL using X-rays

In addition to a physical orthopedic exam, your veterinarian may request x-rays to evaluate your dog's acl for a more thorough overview. Many times the torn ACL in dogs can be appreciated on a lateral X-ray of the knee. If your veterinarian recommends taking X-ray, make sure that they also x-ray the pelvis and hips. This can be a critical part of understanding why your dog injured the leg in the first place. Many times when a dog tears their right acl it is due to a problem in the left hip, and your dog has been compensating on that right leg because the left hip is uncomfortable.

Underlying Reasons for ACL Tears in Dogs

Let's Briefly Look at Some of the Reasons Why There are Cruciate Ligament Injury in Dogs:

  • Obesity: In the United States, it is estimated that 50% of animals are considered overweight. Due to the increased stress that excess weight places on the body, dogs are now more susceptible to joint and ligament injuries than ever before.
  • Lack of Exercise: Due to the fact that people are generally working more and exercising less, this has a direct impact on our pets. It used to be that they were much free to roam about and get exercise on a daily basis. Now, due to stricter leash laws and for safety reasons, when we are not home our dogs are lounging around our houses. They have become, to some extent, "couch potatoes". Lack of exercise means that our muscles and ligaments are not conditioned and therefore they are vulnerable to injury.
  • Genetic Stresses: The term Hip Dysplasia seems to be a very commonly understood concept among large breed dog owners. When a dog has an underlying genetic orthopedic issue early in their life, many times they do not show us their problems or they just not visible to us because they are not overtly limping or crying. Yet because of this weakness, they are subconsciously compensating, using other parts of their body to take some of the stress and weight off of the affected limb. This can also lead to future injury, especially to the knees and back. Ie. ACL tear in dogs
  • Weekend Warrior Syndrome: This explanation of the concept about why dogs frequently injure their ACLs was created here at TopDog. The theory behind it is this: Take into account your dog's overall lack of daily exercise, add in some extra pounds of weight and then a beautiful weekend day when our dogs are outside for extended periods of time being dogs: playing with a ball, visiting a dog park or chasing squirrels in the backyard. It is when our dogs are not properly stretched or conditioned that they injure themselves.
  • Angle of the Joint: Most of the time we never think about the fact that our dogs' knees are always in flexion; i.e. their knees are always bent. Because of this, the ACL ligament is always load-bearing or carrying weight on it, whereas with people this is not the case. We walk for the most part straight on our knees. This is why it is usually football players or basketball players who sustain these kinds of injuries because of the explosion or hyperextension force, which they place on their knees when they are jumping or lunging.

Cruciate Ligament Injury in Dogs can be either a Partial or a Full Tear

Now that you have a better understanding about why so many dogs injure their knee ligaments, you need to understand the difference between a partial and full ACL tear.

We often use the analogy of a steel cable. A steel cable may be made up of 100 individual cable strands. If you were to cut or break 10 of those strands, the overall strength and ability to hold probably would not be affected that much. But if you where to break 50 of those strands, then that would be a different story. Though the cable would continue to hold the weight for some time, at some point in the future it is going to break.

The same holds true for the ACL ligament. Many dogs don't fully tear the ligament all at once. Many of them partially tear it and then over time it leads to a full rupture.

Surgery vs. Rest and Medical Management

There are stories that I am sure you have read online about how a dog ruptured its ACL and then rested its way to full recovery. If this a true scenario, and I stress IF, then it is rare. If a dog is using the limb and fully bearing weight on it, then what could have occurred is this: In some very mild tears where the dog is toe-touching for a few days and then seems to improve with medications, what happens is the body will lay down scar tissue on the outside of the joint to help stabilize the knee.

For all other dogs, meaning moderate partial tears to full tears, this is 100%, hands down, a surgical repair. It is also important to note that many times dogs will have an accompanying meniscus injury at the same time.

Next up: Learn more about TPLO Surgery as an option for treating acl injury in dogs.

How-To Videoson Home Rehab

Dr. James St.Clair shows you everything to do to help your dog from the day you dog gets home through recovery.