FAQ (Frequently Asked Questions)

How does the anatomy of the Canine stifle joint work?

The structure of a dog's stifle joint closely resembles that of a human knee. It comprises two lengthy bones, namely the femur (thigh bone) and the tibia (shin bone), as well as a smaller bone called the patella, which articulate together. The joint's stability is primarily maintained by four ligaments: the cranial cruciate, caudal cruciate, medial collateral, and lateral collateral. Additionally, there are two menisci, medial and lateral, functioning as cushions between the femur and the tibia to provide congruency and enhance overall stability. A notable point of differentiation between the dog's stifle and the human knee lies in the more significant slope at the top of the dog's tibia, known as the tibial plateau slope (TPS).

The cranial cruciate ligament (CCL), equivalent to the anterior cruciate ligament (ACL) in humans, plays a crucial role in restricting the hyperextension of the stifle, controlling the internal rotation of the tibia in relation to the femur, and preventing the forward sliding or drawer motion of the tibia relative to the femur. The rupture of the cranial cruciate ligament (CCLR) stands out as the primary cause of hind limb lameness in dogs.

The underlying cause of CCLR in the majority of dogs differs from ACL injuries in most humans. While trauma commonly causes ACL tears in people, CCLR in dogs is typically degenerative. Various factors have been suggested as potential contributors to cruciate injuries in dogs, including genetics, obesity, poor fitness level, early neutering, excessive tibial plateau slope (TPS), immune-mediated disease, and the presence of bacteria within the joint. The highest risk for CCL tearing exists in young to middle-aged, large breed, female dogs, although any dog can develop CCLR. Similar to ACL tears in humans, acute traumatic ruptures can also occur.

Although the underlying cause of the disease may vary among dogs, the joint's anatomy may play a role in the ongoing breakdown of the ligament. Due to the slope of the top of the tibia, known as the tibial plateau, the cranial cruciate ligament of the dog undergoes stress during weight-bearing, attempting to maintain appropriate alignment between the femur and the tibia. Once the ligament's integrity is compromised, the tibia starts to move forward in relation to the femur during weight-bearing. There is evidence suggesting that the steeper the tibial plateau slope, the higher the likelihood of a dog developing CCLR. The resulting instability contributes significantly to the pain experienced by dogs with this injury. As the cruciate ligament tears, changes also occur in the joint, leading to early cartilage deterioration and, in advanced stages, complete cartilage loss resulting in arthritis. In most cases, once the degenerative process of the CCL begins, the ligament progresses to a complete tear.

How is the problem diagnosed?

Clinical signs of early (partial) CCLR may include an acute onset of hind limb lameness following activity (can be weight bearing or non-weight bearing) that improves with time and is followed by intermittent stiffness after rising or mild to moderate lameness following heavy activity. As the disease advances and the ligament progressively tears, the lameness may become more consistent. Acute complete tears may initially result in a non-weight bearing lameness on the limb, but as time goes on the dog may intermittently use the limb. Instability in the joint associated with CCLR can also lead to injury of the meniscus. Injury of the meniscus can be extremely painful for pets and may, for a period of time, lead to a non-weight bearing lameness.

There are multiple tests your veterinarian can perform to help diagnose a cranial cruciate ligament tear. One of the first signs present prior to instability may be pain with full extension (hyperextension) of the knee. This pain is likely due to stretching of the intact or strained fibers of the cruciate ligament. Once the ligament tears to a certain degree the tibia can be manually manipulated to show instability in what is called the “cranial drawer test” in which the tibia can be moved forward in relation to the femur. Another sign referred to as tibial thrust, may be elicited as well. With this test, weight bearing is mimicked and the front of the tibia can be noted to be pushing forward in relation to the femur. It is important to keep in mind that many patients with clinical signs of pain and lameness may have a partial tear of the CCL. In these cases, there may not be any obvious instability (cranial drawer or tibial thrust) on the exam, however, the patient has a torn CCL that will likely progress to a complete tear.

Other signs that may be noted on the physical exam include loss of muscle mass (atrophy), detection of effusion (swelling) within the joint, and scar tissue formation around the knee (buttress). This scar tissue is the body’s natural response to try and stabilize an unstable joint. Long-term this scar tissue leads to a decreased range of motion in the knee. Finally, a “clicking” sound may be noted in a small percentage of patients with meniscal tears.

Though the cranial cruciate ligament is not visible on an x-ray, radiographs can help confirm a diagnosis of a CCLR by detection of changes that occur in the joint following CCL injury. These changes may include effusion (excess fluid in the stifle), arthritis, and forward movement of the tibia relative to the femur. Radiographs can also help rule out other concurrent injuries.

What are Canine ACL (CCL) Treatment Options?

Patients with cranial cruciate ligament rupture (CCLR) have both medical and surgical treatment options available. Medical management is often considered a more conservative approach compared to surgery. It's essential to recognize, however, that medical management for CCLR in dogs can be extensive and costly. The decision to opt for surgical intervention may be influenced by factors such as the patient's size, the stage of the disease, the level of instability, your expectations regarding your pet's activity level and quality of life, and the presence of any other concurrent medical conditions (such as other orthopedic diseases, severe heart issues, uncontrolled hormonal diseases, cancer, etc.).

What are reasons to opt for TPLO Surgery?

Tibial plateau leveling osteotomy (TPLO) stands as one of the original methods of osteotomy, involving bone cutting, employed to address CCL injuries in dogs. This surgical approach has been in practical use for over two decades, supported by nearly 200 research articles dedicated to its exploration.

During this canine knee surgery, a semi-circular bone cut is executed at the summit of the tibia (shin bone). Subsequently, a small section of bone is rotated by the surgeon to reduce the tibial plateau slope (TPS), typically averaging around 25-30° in dogs, to a target range of approximately 5-7°. Following this adjustment, the two bone segments are secured with a plate and screws until the bone undergoes healing.

Essentially, the procedure involves inducing a controlled fracture and repositioning the bone to achieve a more stable configuration. The rotation and leveling of the tibial plateau aim to hinder the femur from sliding down the slope of the tibia, contributing to the stabilization of the knee.

What does research say about Canine TPLO Surgery?

In spite of the perceived invasiveness associated with this procedure, dogs typically exhibit enough comfort to initiate weight-bearing on the limb within days of the surgery. This swift restoration of function and comfort is a primary factor influencing our preference for TPLO surgery in dogs, surpassing alternatives such as the lateral suture and other techniques.

Recent research has revealed that even in small breed dogs, the return to weight-bearing is more rapid, accompanied by a higher level of functionality with TPLO compared to a less invasive extracapsular repair technique; specifically, lateral imbrication.

When should my vet remove the implants in my dog’s knee?

During the initial 8 weeks following TPLO surgery in dogs, we depend solely on the implants (plate and screws) to provide stability to the surgical site. Once the bone has fully healed, the plate and screws become redundant.

In the majority of cases, the implants are retained unless issues arise, such as infection or irritation. Only 3% of patients undergoing TPLO may require the removal of the plate.

Just remember inform your airport security about the plates and screws in your dog’s knee(s) before taking your canine companion through the metal scanners!

Should I opt for TPLO Surgery for my small-breed canine?

Research endorses the application of TPLO in small-breed dogs, and certain surgeons may favour this approach over the lateral extracapsular suture.

An updated examination of research concerning TPLO and anticipated results for smaller dogs advocates for this procedure due to its ability to achieve sun

• Substantial restoration of limb function

• Minimal lameness

• Reduced incidence of complications

Additionally, this recent study identifies TPLO as a more stable technique for mending a ruptured cranial cruciate ligament in small canines. Many surgeons are now performing TPLO’s on small dogs as they feel these pets, similar to large dogs, have a quicker and more full return to function than with other procedures.

How will TPLO Surgery improve my medium or large breed pet’s condition?

In medium to large breed dogs (>30 pounds), an increasing body of evidence-based literature suggests superior outcomes with TPLO surgery compared to other commonly performed procedures.

For example, in a recent study comparing the long-term results of TPLO and tibial tuberosity advancement (TTA) surgeries, dogs that underwent TPLO exhibited improved mobility and reduced pain. The research also highlighted that this knee surgery for dogs contributed to an enhanced quality of life over time.

Specifically, the study’s authors noted TPLO's positive impact on the following aspects:

• Average pain experienced in the last seven days

• Interference with walking

• Morning stiffness

• Ability to jump and climb

• Limping during mild activities

• Overall quality of life

What can I expect Post-Surgery?

The TPLO procedure is associated with a reported 90-95% rate of good to excellent outcomes. An excellent outcome is characterized by your pet being able to run, jump, and play without any noticeable signs of past issues. In the case of a good outcome, your pet may experience some soreness for a period and might require a brief course of anti-inflammatories after engaging in strenuous activities.

However, for various reasons, approximately 5-10% of patients may not achieve the desired level of functionality. It's crucial to acknowledge that even if your pet encounters complications, such as an infection or a meniscal injury, a good to excellent long-term outcome is still possible, albeit with some challenges along the way.

Is there a time sensitivity to ACL or CCL surgery? What are the consequences of delaying the procedure?

The urgency for ACL surgery falls somewhere in between. While it's not deemed an emergency, most surgeons advise addressing the injury sooner to potentially slow arthritis progression. Moreover, prolonged instability in the knee increases the risk of a meniscal injury over time. Opting for prompt surgery allows your pet to regain comfort and resume normal activities more quickly. If you're uncertain about choosing between medical or surgical management, waiting a few weeks for you and your family to decide typically doesn't significantly alter the long-term outcome.

What are the potential complications of surgery?

Complications linked to TPLO surgery can vary among surgeons. It's crucial to discuss the specific risks associated with your dog's TPLO procedure with your surgeon.

Implant failure, which encompasses bending, breaking, or backing out of screws or the TPLO plate, is fortunately a rare occurrence, happening in less than 2% of cases. Complete failure of fixation is even rarer. Understanding that TPLO surgery involves creating a surgical fracture and stabilizing the bone in a new position is essential. The plate and screws play a vital role in holding the bone together until it heals in this new position. Excessive activity too soon after surgery increases the risk of implant failure. To minimize this risk, it is crucial to strictly adhere to your veterinarian's discharge instructions regarding post-surgery activity levels. Signs of implant failure can range from subtle, such as a single screw breaking, to an acute onset of pain and lameness in the operated limb.

Infection is another potential complication, occurring in approximately 5% of patients after a TPLO procedure. Treatment may involve a short course of antibiotics in some cases, while others may require a more extended antibiotic regimen followed by implant removal. Typically, the bone plate and screws remain in place for your pet's lifetime. However, if an infection arises with persistent lameness, swelling, or drainage from an incision site, your veterinary surgeon might recommend plate removal. The removal occurs only after the bone has fully healed in its new position, ensuring the benefits of the surgery are maintained despite the implant's removal.

Meniscal injury often accompanies ACL injuries, and it may be identified during the TPLO procedure. If a meniscal tear is observed intra-operatively, the torn section is usually removed. If the meniscus is intact, it is generally left in the joint. Despite TPLO stabilization, there remains a possibility of future meniscal tears, with an incidence ranging from approximately 3%-12%. If a meniscus tears post-TPLO, your veterinary surgeon may advise an additional surgery to address the torn portion.

Bruising and swelling are common post-surgery complications, including TPLO. Following your veterinarian's instructions to manage these issues is essential. Swelling around the ankle is often observed 3-5 days after TPLO surgery, lasting approximately a week and resolving on its own.

If both of my dog's ACLs are ruptured, can surgery be performed on both legs simultaneously?

This decision typically depends on the surgeon and can be a challenging choice for both pet owners and veterinary surgeons. What may be suitable for one family may not be optimal for another. Let's examine the advantages and disadvantages.

It is known that around half of patients who tear one ACL may go on to tear the other, and it's not uncommon to find patients with both ligaments ruptured at the time of diagnosis. Opting for surgery on both knees simultaneously entails one anesthetic episode, one surgery, one period of hospitalization, and one rehabilitation period. It is also more cost-effective to perform surgery on both knees at once. However, it is recognized that prolonged anesthesia and surgical times may elevate the risk of surgical site infection. Moreover, if surgery is conducted on both limbs concurrently, your pet essentially lacks a stable leg during the immediate post-operative recovery, making the initial days of recovery challenging for taking your pet outside for restroom breaks. On the other hand, if surgery is done on only one knee, and the other is also affected by a cruciate tear, once the surgical limb begins feeling better (potentially within days following surgery), more weight is placed on the surgical limb, increasing stress on that implant. With bilateral surgery, stress on the implants may be minimized, assuming symmetrical weight-bearing.

While older literature advised caution against performing bilateral TPLOs, recent advancements in implant technology, as indicated by the most recent peer-reviewed literature, show no difference in complication rates between single-session bilateral TPLOs and staged TPLOs.

Does undergoing a TPLO procedure have adverse effects on the other leg?

The concise answer is no, it will not. ACL injuries in dogs typically have a degenerative nature with a significant genetic component. Consequently, it is common for pets to experience tears in both ACLs. Research indicates that 60% of dogs tear the ACL on their "good leg" within two years of the first ACL tear diagnosis. Another study found that up to 15% of pets already had bilateral injuries at the time of diagnosis. When a pet is lame on one leg, they often compensate by bearing more weight on the "good leg," and this weight shift may be challenging to notice. In most cases, the TPLO procedure rapidly facilitates the use of the "bad leg" and aids in weight distribution. If the ACL tears on the "good leg" during the surgical recovery period, it is highly likely that it was already in the process of tearing before the surgery.

Are x-rays required prior to surgery?

Certainly. X-rays of the knee are necessary before the surgery to measure the tibial plateau angle, crucial for determining the required rotation of the small top segment of the tibia. This x-ray is usually most effective when performed on a sedated patient, allowing for precise patient positioning.

Is bloodwork always required prior to surgery?

In many instances, yes. Most dogs with ACL tears are content, well, and in their middle-aged years. Nevertheless, understanding a patient's overall health is crucial before anesthesia. Blood work enables your veterinarian to assess specific vital organ functions before administering medications that can influence the body's physiology.

Will my dog suffer during the post-operative recovery period?

TPLO surgery is a procedure with a significant level of invasiveness. Fortunately, the effective utilization of opioids like morphine, along with other medications, proves highly successful in preventing and managing post-operative pain. Moreover, many surgeons employ epidurals and local anesthetics to ensure the comfort of pets during the recovery process.