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Ligament Tears and ACL Surgery

By Dr. Jason McLeod

Clinic Principal of both Algonquin and Bracebridge Animal Hospitals

Many people don’t realize their dogs can tear their knee ligaments just like people. The most common ligament tears are those that involve the cranial (or anterior) cruciate ligament (CCL or ACL). The sad thing is that many of these dogs were not doing anything athletic when the tear occurred, unlike in people. If you did not know your dog could have such an injury then you simply need to ask a handful of dog owners and you are sure to receive a quick synopsis of the condition, as it is by far the most common hind leg injury in dogs. An estimated $1 billion dollars are spent every year in the United States on repairing ACL deficient knees in dogs.

Why do we refer to the possible surgical interventions as ‘repairing ACL deficiencies’? It’s now widely understood that many dogs, of various breeds, actually have a gradual degeneration of the cranial cruciate ligament that ultimately ends in failure or tearing. Sometimes this appears as a sudden, painful lameness and other times the owners are unaware their dogs have such a catastrophic injury because it happened so gradually and owners simply attribute the increasing lameness to ‘old age’. No one really knows the percentage of dogs that suffer traumatic acute tears (those that occur because of a high force injury with no previous ligament degeneration) versus those that have the progressive degenerative tears. Scientific studies support that as many as 75% of dogs may have degenerative tears even if they are not identified as such at initial diagnosis.

Many different breeds of dogs have now been identified as high risk breeds such as Mastiffs, Staffordshire Terriers, Akitas, Rottweilers, Golden Retrievers, Labrador Retrievers, and even Cocker Spaniels. In the past, this statistical prevalence of certain breeds was often attributed to conformation and muscularity of some breeds such as Rottweilers and Mastiffs. However, it is now widely accepted there are numerous factors involved in the relationship of certain breeds and their prevalence of ACL tears. Some breeds, such as Golden Retrievers, are extremely common breeds because of their numerous traits that make them ideal pets for so many of the pet-owning population. It was often thought retrievers were more commonly seen simply because they were more commonly owned! We now know there are genetic factors involved as some breeds, such as Greyhounds, rarely tear their ACLs despite their high impact and demanding athletic lifestyles.

Over the years many surgical procedures have been developed to aid in stabilizing the knee with a goal of returning the dog to normal functioning of the hind limb.

If your dog is diagnosed with an ACL tear it is ideal, in almost all cases, for any breed of dog, of any age, to have a surgical repair to help with the loss of stability in the knee that occurs when the ACL ruptures. This ligament is instrumental in stabilization of the knee (and the entire hind limb) during standing, walking, running and jumping. Dogs that do not have repairs performed will invariably develop significant osteoarthritis and in most cases, moderate to marked lameness. Over time, this lameness appears as a decrease in the flexibility of the knee joint (and hence the entire hind limb), mobility, and strength and results in a decreased ability to perform activity.

Over the years many surgical procedures have been developed to aid in stabilizing the knee with a goal of returning the dog to normal functioning of the hind limb. Several different techniques that relied on the same principles have been adapted over the past several decades that essentially create a ‘false ligament’ that’s used for stabilization. This ligament was usually of some kind of wire, suture material, or nylon. Although these surgical techniques were the most utilized and many pets regained excellent post-operative function, they all had inherent problems, especially with implant loosening or failure, and in most cases a moderate to substantial decrease in the comfortable flexibility of the leg.

Over the past 10 years, techniques have come into common practice that utilize physics and mathematics in a very intriguing way to overcome the abnormal forces that occur in the knee joint when the ACL is torn. These techniques focus on determining the ideal way to change the angle of the tibial plateau to neutralize the forces occurring during standing, walking, and jumping. The tibial plateau is the top surface of the shin bone (tibia) that is essentially in contact with the femur (thigh bone) within the knee joint. By changing the angle of the tibial plateau, the forces that were controlled by the anterior cruciate ligament are no longer of concern and the pet can walk with no discomfort or abnormal forces occurring within the knee joint. These techniques involve bone plating and are very strong surgical repairs for a joint that is under a great deal of stress during every day activity. The most commonly used techniques are the Tibial Plateau Leveling Osteotomy (TPLO) and the Tibial Tuberosity Advancement (TTA). Although these surgical repairs are different in their approach, they are essentially utilizing the same principles to achieve stability for the knee joint and are considered the surgical repairs of choice for numerous reasons. They both are repairs that are extremely strong and essentially lead to immediate stability for the dog thus allowing for very quick recoveries post-operatively. This is a win-win for pets undergoing the surgery and for the owners who are responsible for the post-operative care. 

Many people are very intimidated by the prospect of such a surgery for their dogs. In my experience, much of this trepidation occurs because of what is feared during the recovery phase. Owners are often most worried about something going wrong once the pet comes home, not the actual surgery itself. While the recovery period is not short, with the more stable bone plating techniques, most pets require no assistance of any kind and are essentially 100% in terms of healing by 8-10 weeks post-operatively. If other techniques are used, recovery can take at least six months although the effort required of the owner decreases proportionately with time post-operatively. Initially owners need to expect they will be essential in helping their pet to go outside for bathroom breaks, icing, massage and easy to perform physiotherapy. As time progresses, usually by about 10 days post-operatively, becomes more a focus on walking exercises with the focus on determining ways to help build strength. We utilize many techniques in the home, from sit-to-stand exercises and stepping over low bars or blocks, to figure-eight and circle walking outdoors. Of course, in our region of beautiful forests and snowy winters, we utilize ankle deep snow and uneven forest trails for much of the physiotherapy. For our city dwelling clients, I advise them to use their imagination with curbs and sidewalks, and strolls through city parks. Summer can be ideal for physiotherapy as swimming in a pool or lake is ideal if owners cannot frequent hydrotherapy pools.

Whatever the case, the physiotherapy is invariably a way for owners to connect with their pets and be an integral part in their recovery. In my experience, most owners are quickly delighted in how simple the physiotherapy actually is and how much is can be an excellent way to reconnect with a pet in our busy lives. Being focused and dedicated during the post operative period always allows for a better recovery for your pet and I often iterate to owners that the surgery itself is only part of the journey.

Don’t be dismayed if your pet has an ACL tear. Dogs can lead a perfectly normal life with proper care and it does not take an expert to care for them at home. If you don’t believe me, just ask the 65-year-old widow that weighed 100 lbs and cared for her 135 lb dog that I did surgery on. She did just fine all by herself.