by Kristin Kirkby Shaw, DVM, MS, PhD, CCRT, DACVS, DACVSMR
Published: 1/3/2020
As a surgeon and rehabilitation specialist, one of the most common questions I am asked from pet owners and fellow veterinarians is “Can I manage cranial cruciate ligament (CCL) rupture without surgery?”
Well, the simple answer is, yes—CCL rupture is not a life-threatening condition requiring urgent surgical intervention. Plenty of dogs out there tear their CCL and never see a veterinarian, let alone a surgeon. And many dogs that present to a surgeon with a CCL tear are not surgical candidates.
However, I do believe that surgery is the best option for achieving optimal function and minimizing the progression of arthritis. Even this comment is too simple though. So I would like to explain my evolution in approaching CCL injuries and review the pathophysiology (or what we think we know) of CCL disease and rupture. Then I will share my current approach to treating dogs with CCL injuries.
My CCL Journey
I became a certified rehabilitation therapist in 2008, during my final year of surgical residency. This is not common– a surgical residency alone gives you plenty to focus on. But I knew that while I had the honor of being in one of the most prestigious surgical training programs in the world, something was missing. If the orthopedic condition we were seeing did not have a surgery to “fix” it, we simply recommended rest and pain medication. This was in the mid-2000s, the early days of canine rehab, and we did not have anyone to refer cases to that were not surgical.
I knew the benefits of physical therapy first hand. When I was a rotating intern, I took up running. Prior to this, I had been a dancer and involved heavily in martial arts and boxing. So when I starting running, my body was subjected to forces that were unfamiliar, and I developed severe pain on the outside of my knee. I went to an orthopedic surgeon, whose conclusion was that my tibias (shins) are bowed and if I want to continue running, I would need corrective osteotomies (cutting the bones and realigning them), or I should just not run.
While I was only a “baby doctor,” 6 months out of vet school, I knew that this just didn’t seem right. (And for the record, my tibias are not noticeably bowed!). So I got a second opinion from a physical therapist, who diagnosed me with ilial-tibial band syndrome (ie, inflammation of the fascia lata on the outside of the knee), which is only the most common new-runner injury! I had an imbalance of strength between my quadriceps and hamstring muscles. Physical therapy, including strengthening and foam rolling, enabled me to continue running (I’ve run a marathon and multiple half marathons) and avoid surgery.
So, fast forward a couple of years and now I am an orthopedic surgery resident faced with dogs with conditions that weren’t clearly surgical, and I had nothing to offer them. Or, I was seeing dogs with partial CCL tears, and I was offering them a tibial osteotomy for treatment. I really wanted to know if there was something else we could be doing. I dove headfirst into canine rehab, attending both the University of Tennessee and Canine Rehabilitation Institute programs. I took graduate classes at the University of Florida in exercise science, biomechanics, and therapeutic modalities. I founded the University of Florida Small Animal Hospital Rehabilitation Department. We started having options for dogs that didn’t need surgery and provided therapy for dogs recovering from surgery. But what about CCL tears?
As a young rehab therapist and newly-boarded surgeon, I naively, idealistically and somewhat smugly thought, “How dare those surgeons perform a TPLO on a dog with a partial CCL tear! I can strengthen that dog’s hamstring muscles and help him and the owners avoid surgery and keep him active.” Sigh. I wish it were that simple. Let’s now review CCL disease pathophysiology:
CCL Disease
CCL “disorders” are the most common cause of lameness in dogs. I use the word “disorder” to include all of the different descriptive terms we may use: rupture, tear, deficiency, disease, injury, and sprain. There is not a consensus among surgeons as to which of these descriptors is preferred. They are all somewhat accurate and I do not want to get too far into the weeds here. However, it is important to realize that this condition is not as simple as an injury, rupture, or tear. CCL Disease may be the most accurate all-encompassing terminology because the condition involves a spectrum of disruption to the ligament and joint.
The underlying cause of CCL Disease is still not fully understood. There are many review articles on this topic, and I will not get into all of the details here. It is well accepted that traumatic injury of the CCL is rare in dogs. For the sake of this discussion, I am referring to the more common degenerative CCL condition that we frequently see in veterinary patients. There are combinations of biomechanical deficiencies and biological processes that result in the CCL being weaker than it should be or at risk of degeneration. Synovitis and joint inflammation are believed to precede CCL tearing, not simply be the result of it.
Once the CCL begins to degenerate, its function is compromised. This is when the words deficiency and sprain become relevant. Early in the CCL disease process, there may not be significant macroscopic disruption of the ligament; however, microscopic degeneration is present and ligament fibers may be stretched or otherwise abnormal. This can be referred to as a Grade 1 Sprain.
When the CCL is compromised, mechanoreceptors within the CCL provide feedback to the surrounding muscles that CCL function is deficient. This results in quadriceps inhibition and atrophy; concurrently, synovitis leads to effusion. Consequently, we see intermittent lameness and discomfort with full extension of the stifle. There is no instability of the joint (no cranial drawer or tibial thrust), but the dog may react when we perform these tests. This is because the CCL is responsible for preventing stifle hyperextension and cranial tibial subluxation. When the ligament is stretched to the point where mechanoreceptors recognize function is deficient, the result is the body’s protective instinct, which we see as a pain or discomfort reaction.
Continued degeneration of the CCL leads to Grade 2 Sprain or a partial tearing of the ligament. In these cases, we can often palpate instability when the stifle is held in flexion. Full extension continues to elicit pain or a protective reaction. Ultimately, the condition may progress fully to a Grade 3 Sprain, also known as a complete tear or full rupture of the ligament. At this point, depending on the chronicity and established periarticular fibrosis, gross instability of the joint is palpated (positive cranial drawer and tibial thrust).
Complete rupture of the CCL will lead to osteoarthritis (OA) in virtually every animal. (As mentioned, there is often inflammation preceding CCL rupture, so complete rupture results in progression of OA). In fact, the experimental transection of the CCL, called the Pond-Nuki Model, is a common model used to evaluate treatments for OA. Meniscal injury is common (up to 80% of cases) with CCL rupture; the more unstable the joint, the more likely the meniscus will be torn. Meniscal injury leads to further pain and more severe OA.
The goals for treating a dog with CCL Disease are to minimize the progression of OA (and associated pain) and return them to the highest level of activity possible. To do this, we must address the inflammation within the joint and overcome the abnormal biomechanical forces due to CCL deficiency. To be very clear, the CCL will not heal back together once it is ruptured. And to date, there is no conclusive long term evidence to show that even a Grade 1 Sprain will return to normal, even after treatments with biologic therapies such as platelet-rich plasma or stem cells. The body’s natural response to CCL rupture is to attempt to provide stability through peri-articular fibrosis (ie, medial buttress). Given time (years), this process is successful, cranial tibial subluxation (palpation of tibial thrust) is virtually eliminated. But, OA is often quite significant in these cases.
So, what is the optimal treatment? Can we intervene non-surgically in Grade 1 CCL Sprain and avoid surgery? There are a lot of opinions out there—here is mine…
Coming Full Circle
I spent several years trying to manage “early partial CCL tears” using rehab alone. These were cases that had joint effusion and discomfort with stifle extension but did not have instability, thus, Grade 1 Sprains. Even in those days, I did recommend surgery for any dog with joint instability. More on surgery soon.
My approach to non-surgical management of Grade 1 CCL Sprains included addressing inflammation (NSAIDs, laser, ice, omega-3 rich diet), chondroprotectants (Adequan), and therapeutic exercises that included strengthening and proprioception (UWTM and land-based). And very importantly, activity restrictions. I did not use braces or routinely use intra-articular therapies. We had several “success” cases in which we restored muscle mass and reduced inflammation and pain. In fact one dog even made it to Westminster!
But ultimately, after months of therapy, once we finally allowed the dogs to return to full activity, they would inevitably return with lameness again. Sometimes very quickly, sometimes months to years later. Even the Westminster dog eventually wound up having bilateral TPLOs.
Even in the best-case scenario, ligaments take a VERY long time to heal. As in 9-12 months. Perhaps why I was not able to achieve ultimate success with non-surgical management is that my protocols were not quite right, or that I wasn’t using the right form of “regenerative” medicine. But I believe that expecting a dog to completely avoid activity that may compromise the healing of the ligament for a full year is unrealistic. Furthermore, the more we learn about CCL disease, the expectation for healing or normalizing may just not be reasonable.
Therefore, my approach and philosophy for managing CCL disease have completely evolved or come full circle back to my surgical roots. I know that surgery is a big deal, not without risks and potential complications. But it is, in my experience and opinion, the fastest, most reliable, and most evidence-based means of managing CCL disease. Again, this is not to say that there are dogs for which surgery is not the right choice- for medical, financial or practical reasons. And for these dogs, I do offer rehabilitation and pain management. However, my staff and I find these to be among the most challenging rehab cases.
I now feel that dogs that have evidence of Grade 1 sprain—joint effusion on radiographs and pain with stifle extension are candidates for surgery. I continue to feel that dogs with any instability (Grade 2-3, aka partial or complete tears) are best served with surgery. Surgery provides a very predictable recovery period, much shorter than what would be needed for peri-articular fibrosis or ligament healing. Surgical intervention prior to meniscal injury will greatly reduce the risk of meniscal tears and more substantial OA. Surgical intervention prior to significant muscle atrophy will also improve recovery and long term function. And ultimately, I do feel that surgery can reduce the progression of OA, especially if it is performed early in the disease course.
Now, what is the best surgery? In my hands, it is the TPLO. I am confident in my technique and happy with the clinical results. I work alongside other surgeons who have the same opinion and outcomes. But get 100 surgeons together and you probably won’t have 100% agreement. There are several studies comparing outcomes between TPLO, TTA and lateral suture techniques (including Tight Rope). To date, the TPLO has the most evidence supporting its superiority. But in the right case selection, other techniques can be successful. Ultimately, I don’t think that we as a surgical profession have figured out the optimal treatment for CCL disease. But if (or when) it was my dog, I would opt for TPLO early in the CCL disease process, and follow with a comprehensive post-op rehab plan. For more on post-op rehab, read this.
Reviewed/updated
12/2024