Trek Veterinary Surgery
Jeremiah D. Moorer, DVM, Diplomate ACVS
The cranial cruciate ligament is an important stabilizer within the knee joint (stifle) of dogs and cats. It is analogous to the human anterior cruciate ligament (ACL). You will sometimes hear these terms interchanged when referring to dogs.
Another important stabilizer in the stifle is the menisci. These also function as “shock-absorbers” in the stifle and are often torn or damaged at the time of the cruciate ligament tear.
What is cranial cruciate ligament disease?
Cranial cruciate ligament disease often refers to the process that causes the cruciate ligament to tear or rupture. The underlying reason is not entirely understood but is a multimodal disease process that can include anatomic variations and the slope of the tibial tuberosity. Other contributing factors include ligament degeneration, obesity, poor physical condition, genetics, conformation, and breed. Cruciate disease is often thought of as a disease of large breed dogs. While it is true that large breed dogs are more prevalent, small and medium breed dogs are often affected as well.
Cranial cruciate ligament tears are the most common cause of lameness (limping) in dogs. Many cruciate tears start off a partial tear of the ligament but most often progress to a complete tear unless surgical stabilization is performed prior to the progression. Meniscal injury is less frequent with partial tears of the cruciate ligament due to some degree of inherent stability provided by the intact cruciate ligament fibers.
Because this is a degenerative condition, approximately 40-60% of dogs that tear one cruciate ligament may tear the other side. This occurs, on average, within two years.
How do I know if my dog has a torn cranial cruciate ligament?
Limping in one or both back legs can be the first sign of a cranial cruciate ligament tear. While there are certainly other causes of lameness (limping), cruciate ligament tear is the most common cause. Age, breed, and history are all taken into consideration, in addition to a physical examination by your veterinarian, when diagnosing a cruciate ligament tear.
Radiographs (x-rays) are often used as an adjunct diagnostic to evaluate for the degree of arthritis, presence of effusion (fluid swelling) in the joint, and to rule out other causes of lameness, including fracture or cancer of the bone. Direct examination of the cruciate ligament, with arthroscopy or arthrotomy, is the gold standard of diagnosing a tear of the cruciate ligament. The meniscus is also examined at that time to evaluate for any injury or tearing.
While MRI is a frequent diagnostic used in diagnosing ACL tears in humans, the canine stifle anatomy is much smaller, which can make it difficult to accurately diagnose the cruciate ligament tear and meniscal injuries. In addition to the anatomic differences, dogs must be anesthetized for the MRI, which adds to the cost and morbidity associated with this diagnostic tool. An MRI may be needed if a neurologic cause for the lameness needs to be ruled out prior to addressing any orthopedic abnormalities. Veterinary surgeons often work with veterinary neurologists to decide the best course of treatment for your pet.
What surgery will be recommended for my dog?
The first decision that must be made is whether surgery is the best treatment for your pet. The vast majority of dogs require surgical stabilization of the stifle to achieve the best outcome. However, surgery may not be recommended if your pet has other significant comorbidities that preclude surgery or anesthesia. Or, if you and your veterinarian decide to pursue other avenues of treatment. But, as stated before, surgery is most often recommended to give the best long-term outcome.
Every patient is unique, and your veterinarian/surgeon will determine the best procedure for your pet. The Tibial Plateau Leveling Osteotomy (TPLO) has been shown to have the best, and most consistent, outcome of all of the described procedures for cruciate ligament tears in dogs.
What is a TPLO?
Tibial Plateau Leveling Osteotomy (TPLO) is an osteotomy-based, geometry modifying procedure designed to decrease the slope of the tibial plateau to eliminate the instability (cranial tibial thrust or caudal femoral subluxation) associated with the cranial cruciate ligament tear. This is done by making a semi-circular cut in the proximal (near the knee) aspect of the tibia. After this cut is made, the proximal portion is rotated a specific amount to decrease the tibial plateau angle (TPA) to reach 0-6 degrees of slope. Often, the pre-operative slope is between 22-30 degrees. Once the rotation is performed, a plate and screws are placed on the tibia to stabilize the bone and allow it to heal.
Can my dog live with a torn cranial cruciate ligament?
This is a common and very prudent question. Dogs can live with a torn cranial cruciate ligament. The body will try to form scar tissue to stabilize the knee, but often there is residual instability that leads to an increased progression of arthritis compared to after surgical stabilization. If the meniscus is also torn, this can lead to more dysfunction muscle atrophy due to decreased use of the limb. In general, without treatment, there will likely be more progressive arthritis, less limb use, and more muscle atrophy over time.
What is recovery like after TPLO?
The goal after the TPLO is to allow the bone to heal, while simultaneously improving the use of the limb and minimizing secondary soft tissue abnormalities. This is achieved with a combination of activity restriction, at-home exercises, and professional rehabilitation therapy.
In the first 1-3 days, your dog may not want to use the leg much and may hold it up. That is ok during this time period. After this, your pet should start to touch the toes down and increase the amount of weight-bearing in the limb on a daily basis over the next several weeks.
You will likely recheck with your veterinarian at 10-14 days to make sure the incision is healed and to monitor your pet’s progress. It is around this time that your pet should have a consultation with a professional canine rehabilitation practitioner to evaluate the progress and to advise you on exercises to perform at home in addition to the professional therapy.
At eight weeks after surgery, radiographs (x-rays) will be taken of the limb to evaluate for healing of the bone. Many times, the bone is healed enough to be able to increase the activity level of your pet. Depending on your pet’s progress and the degree of bone healing, this may be the only recheck needed for radiographs. If the bone is not sufficiently healing, then one more set of radiographs must be taken at 12-16 weeks to document the healing of the bone prior to returning to a more normal activity level.
How long does it take to do TPLO surgery?
The total anesthetic time for a TPLO procedure ranges from 1.5-2 hours depending on the specific patient. The surgery itself ranges from 45min to 1 hour.
Will my dog need TPLO surgery again?
The incidence of needing repeat surgery on the same leg that has had a TPLO is very low. The main causes for this would include a post liminary meniscal injury (2-8%), implant associated infection requiring removal of the implants (<2%), or implant breakage requiring addition stabilization.
There is, however, a 40%-60% chance of developing a rupture of the other cranial cruciate ligament. This often requires a TPLO procedure on that limb as well. This typically occurs within two years of the first cruciate ligament rupture.
Can cats rupture their cranial cruciate ligament?
Cats can rupture their cruciate ligament, but much less commonly than dogs. Many times cats do not require surgery and can be treated with rest and pain medications. Exceptions to this are cats that do not improve with six weeks of rest and pain medications (as needed) or cats that have concurrent meniscal injury.
Does pet insurance cover TPLO surgery?
Many pet insurance companies will cover a portion of the cost of the TPLO surgery. Eligibility depends on your company and your specific policy.