Knee injuries in dogs
If you asked a group of veterinarians or rehabilitation practitioners to name the most common orthopedic injury that they treat in dogs, I would be willing to bet that 10/10 of them (including us) would say cranial cruciate ligament ruptures. So we are going to break it down and discuss everything you need to know about the dog’s cranial cruciate ligament, including what it is, risk factors for injury, what you can do to help minimize the risk, and options for recovery.
Structure and function of the cranial cruciate ligament
The dog’s cranial cruciate ligament (CCL) is analogous to the anterior cruciate ligament (ACL) in humans, and along with its partner the caudal cruciate ligament, form a criss cross pattern attaching the thigh bone (femur) to the shin bone (tibia). The function of the CCL is 3-fold: to prevent forward displacement of the tibia during weight bearing, to limit hyperextension of the knee and to prevent internal rotation of the tibia relative to the femur (1,2).
Development of cranial cruciate ligament disease
In both dogs and people the cruciate ligament is prone to strain or rupture, however unlike in people who tend to rupture their ACLs traumatically (think of the football player who gets tackled causing the knee to go one way and the foot to go the other way), in dogs CCL ruptures tend to be more of a degenerative condition (think of the ligament as a thin rope that slowly frays over time). Also unlike in people, dogs can have varying degrees of strain/rupture ranging from an early partial tear to a complete tearing of the entire ligament. For that reason these injuries can be tricky to diagnose, particularly when the only clinical sign that the dog presents with is a history of intermittent limping or lameness on one of the hind limbs.
The joint surface of the dog’s tibia is sloped therefore any disruption to the integrity of the CCL allows the tibia to slide forward relative to the femur, and causes repetitive rubbing of the two joint surfaces with each step that the dog takes. This instability of the knee often leads to joint inflammation and pain, which over time can lead to the development of a limp or lameness on the affected leg. Chronic inflammation subsequently leads to the development of osteoarthritis and can additionally lead to damage of other important structures in the knee, namely the shock absorbing meniscus - a cartilaginous tissue that partially divides the surfaces of the knee joint and assists in the distribution of weight bearing forces of the joint (1,2). While the knee contains two menisci (medial and lateral), it is the medial meniscus that tends to be most commonly affected as a sequela to CCL disease. Damage to the medial meniscus can further substantially increase pain in the joint leading to a noticeable increase in lameness, and can also expedite the progression of osteoarthritis.
While there are certain clinical exam findings, biomechanical tests and radiographic signs that are highly suggestive of CCL rupture, it is important for veterinarians to recognize that the absence of any or all of these signs does not exclude a CCL tear, and this should be at the top of the list of rule outs for any dog presenting with a history of hind limb lameness.
Risk factors for the development of cranial cruciate ligament disease
OBESITY - Bolded and capitalized for a reason. Dogs that are overweight are at a higher risk for most degenerative and chronic diseases, including CCL rupture. If there was only one thing that I could recommend to extend the longevity and quality of your pet’s life, it would be to get the excess weight off.
Size - Large and giant breed dogs are predisposed, probably in large part because of the above. However smaller dogs can also be affected.
Spaying and neutering - While there does seem to be a correlation between dogs that have been spayed or neutered and an increased incidence of CCL rupture, that doesn’t mean that everyone should stop spaying and neutering their pets. The number of benefits of spaying and neutering still far outweigh the risks for most pets so have an educated discussion with your veterinarian.
Abnormal joint or limb conformation and biomechanics - Any orthopedic condition, be it developmental or traumatic, that changes the conformation or biomechanics of the knee will put excessive strain on the cranial cruciate ligament. Two of the more common developmental conditions that can predispose a dog to CCL rupture down the road are hip dysplasia and patellar luxation.
High intensity and/or uncontrolled activity - Any dog that has underlying orthopedic disease or arthritis is going to exacerbate that disease with high intensity activities, plain and simple. While dog parks and zoomies might be great for cardiovascular fitness, they put a tremendous amount of strain on the joints and will pretty quickly help to identify the weakest link. Moderate intensity, controlled exercise (aka leash walks) are the best exercise for your dog’s cardiovascular, musculoskeletal and mental health. And they’re not bad for owners as well!
Unfortunately there is no sure fire way to prevent a CCL tear in your dog; part of it comes down to straight up genetics. But there are a few things that are within your control that can help to minimize the risk by making small lifestyle modifications. Keeping your dog at a lean body weight, talking to your vet about the best time to spay or neuter your pet, and sticking to moderate intensity, controlled exercise can go a long way in keeping your dog’s joints healthy well into their senior years.
Treatment options for cranial cruciate ligament rupture
Okay, so your dog has been diagnosed with a ruptured CCL….now what?
Repair of a torn cruciate ligament can go one of two ways - either surgically or conservatively. Discussion about the ins and outs of each surgical procedure are beyond the scope of this blog post, but the decision to go with surgery versus conservative management largely depends on a patient’s age, size, conformation, activity level, lifestyle, and concurrent medical conditions. So let’s skip ahead to the goals of treatment for both surgical and conservative management.
Surgical management
The biggest goal of surgical management is to immediately stabilize the knee to minimize any bone on bone movement between the femur and tibia. Depending on the type of surgery, there may additionally be an opportunity to visualize the menisci arthroscopically and if a tear is identified, to remove part or all of the damaged meniscus at the time of surgery. Recovery time after surgery is generally 8-12 weeks and during that time a structured rehabilitation program can be introduced to improve the dog’s return to function. Goals of post-operative rehabilitation include ensuring that the dog is using the affected limb appropriately, monitoring for and treating pain, addressing any secondary musculoskeletal compensations that may have developed as a result of the lameness, and overseeing a safe and gradual return to activity.
Downsides of surgery are common to most surgeries; risk of infection, implant failure, and risks associated with anesthesia are all rare complications of surgery that we discuss with owners. Additionally cost, age, other medical conditions and the temperament of the dog may be other considerations that will factor into the decision about whether or not to take the dog to surgery.
Conservative management
While the end goals of conservative management may be the same as with surgical management (namely to return the dog to full function), the path to get there may be slightly different. Unlike in a post-operative case where the knee has already been stabilized, in a non-surgical case we have to keep in mind that there may continue to be some instability in the knee while we wait for the body to do its thing and lay down scar tissue around the joint. This can take anywhere from a few months to more than a year, so owners need to be made aware that although the conservative management route is less invasive, it can be a longer commitment. Depending on the size of dog and degree of instability, we may also discuss the addition of a brace to further support the dog’s knee while it heals. Pain and weight management are two critical components of a successful rehabilitation program and are often among the first aspects of recovery that we address with medication and diet changes if needed. Other non-surgical options for managing pain, decreasing inflammation and reducing healing time include therapeutic laser, acupuncture, extracorporeal shockwave therapy, electrical stimulation, heat/cold therapy and hydrotherapy. However at the core of every rehabilitation program is a therapeutic exercise program specifically tailored to the needs of each individual patient based on their discomfort, degree of injury and areas of secondary compensation. No two dogs are alike and their rehab programs should reflect that, keeping in mind that the exercises that we prescribe have to be both appropriate for the patient and manageable for the owner to do at home.
The biggest downside of conservative management of CCL rupture is the additional time that it takes for the knee to heal. We are always evaluating and re-evaluating the patient’s progress and addressing any new areas of compensation or strain as needed. Cost is often a factor when deciding whether to pursue surgery, however owners should be aware that although the cost of surgery is higher up front, several months of rehabilitation can also add up over time and may not necessarily be the less costly option in the end.
In conclusion….
Rehabilitation is a great treatment option for reducing pain, decreasing inflammation and reducing the time that it takes to get your pet back to their regular level of activity in both surgical and non-surgical CCL rupture cases. If your dog has suffered an injury get in touch with us to discuss how we can help your pet regain their strength and mobility to get back to doing all of the things that you love to do together.
Fox, SM (2017) Multimodal management of canine osteoarthritis. 2nd Ed. CRC Press.
Millis, DL & Levine D (2014) Canine rehabilitation and physical therapy. 2nd Ed. Elsevier Saunders.