Canine ACL Injuries: Why do they happen? What are your treatment options?

How many of my readers today have torn their ACL ligament? If so, you know how fast it can happen, and how much it hurts. Dogs experience the same thing. It’s unfortunately an all too common reason for medium and large breed dogs to come in and see me.

First, WHAT is the ACL? The ACL ligament is the Anterior Cruciate Ligament, and it is found in our knee.

Courtesy: Shelbourne Knee Center

In fact, there are two ligaments there that provide stability in the knee joint: the ACL and the CCL (Caudal Cruciate Ligament). Humans and dogs rarely rupture the CCL, but it can happen. These two ligaments form an “X” shape in the knee, and allow us to do all sorts of crazy movements with our legs.

Next, how does an ACL rupture happen? This is usually an injury that happens when the knee is abruptly turned at a high rate of speed.

Think of the dog out running full speed that suddenly switches directions to catch that squirrel or that frisbee. Those high speed 90 degree turns are usually the cause of the ligament to rupture.  The ligament just cannot withstand the force of a turn at high speeds.

My suspicion for an ACL rupture is high when I see a dog who is “toe-touching” lame. This means the dog is walking primarily on three legs, but will barely touch the affected leg to the ground to hop off of it.

During my physical exam I am looking for a couple of things. First, as I hold my hand at the front of the knee while flexing and extending the joint, I will often feel a big “click” as I am going through the range of motion with the joint. Next, with the dog laying on his/her side, I check for a “cranial drawer” in the joint. With one hand firmly holding above the knee on the femur, and the other hand firmly holding below the knee on the tibia, I attempt to move those hands in opposite directions. A normal knee should not move at all, but a knee with a cruciate injury will have movement.

The next step is to take an x-ray. I tell all of my clients that I will NOT be able to see the ligament on this x-ray. Rather I am looking at the angle at which the femur is sitting compared to the tibia. This will often be highly suggestive of an ACL rupture within the knee joint.

Courtesy: DVM360

What do we do once we confirm an ACL injury in a dog? Well, size matters. For some small dogs, rest may be all that the owner chooses to do. The joint will stabilize a little over time, and will definitely become arthritic, but the demands on the joint in a dog that is tiny are very different than the demands placed on the joint in a large or giant breed dog. For all medium, large and giant breed dogs, I recommend surgical repair. While the joint will still become arthritic over time, surgery is the best way to regain the stability necessary in the joint for the normal activities of larger dogs.

Courtesy: Colorado State University

The first surgical option is an Extracapsular Repair. In this method, the Veterinary Surgeon will first make an incision into the knee joint to trim the loose piece of ligament and assess the meniscus on both sides of the joint. These are pieces of cartilage that sit between the femur and tibia for cushioning, and they are often also torn during this injury. The knee joint capsule is then closed. Then a VERY strong line of suture is passed through the front of the tibia bone and around behind the knee joint. This “recreates” the ligament in a new way. It is run in the same alignment as the original ligament, just in a slightly different location. The skin is then closed over the suture.  Recovery time is typically 8 weeks, and dogs must be kept very quiet during this time and slowly re-introduced to exercise on a strict schedule provided by their surgeon.

Courtesy: Colorado State University

The second option is a Tibial Tuberosity Advancement (TTA). After incising into the joint capsule to trim the torn ligament and check the meniscus, the joint capsule is again closed. Next, a vertical incision is made in the front of the tibia bone. The front piece of bone is moved forward and a plate and screws are placed between the tibia and that piece. This changes the angle at which the femur meets the tibia, re-stabilizing the joint. Recovery time is typically 8 weeks, and dogs must be kept very quiet during this time and slowly re-introduced to exercise on a strict schedule provided by their surgeon.

The third option is a Tibial Plateau Leveling Osteotomy (TPLO). This is one of the best options for large and giant breed dogs.

Courtesy: Animal Surgical And Orthopedic Center

It provides superior support at the joint, and the repair is unlikely to “fail.” After incising into the joint capsule to trim the torn ligament and check the meniscus, the joint capsule is again closed. Next, a semi-circular cut is made in the top of the tibia bone. This piece of bone is then rotated downward and reattached with a plate and screws. Just like in the TTA, this method changes the angle at which the femur meets the tibia, re-stabilizing the joint. Recovery time is typically 8 weeks, and dogs must be kept very quiet during this time and slowly re-introduced to exercise on a strict schedule provided by their surgeon.

Finally, a newer method as I write this post is a CORA Based Leveling Osteotomy (CBLO). This method combines the advantages of the TTA and the TPLO.

Courtesy: Wiley Online Library

Which surgery is best for your dog? Only you and your Veterinary Surgeon can decide that together. Your decision may be based on the size of your dog, their activity level, their age, and of course cost. It is best, though, to have surgery done as early as possible. The longer you wait, the more arthritis in the joint, and the less favorable the outcome.  One last piece of information: Dogs who rupture one ACL ligament, will often rupture the other leg's ACL ligament a short time later......