| The knee is a complex joint composed of several key structures. It includes the femur (thigh bone), tibia (shin bone), patella (kneecap), and the small, bean-shaped fabellae at the back. Between the femur and tibia are the medial and lateral menisci—cartilage pads that serve as cushions. A network of ligaments secures the joint, enabling proper movement while preventing excessive or unnatural bending. Inside the knee joint, two cruciate ligaments cross each other: the cranial cruciate ligament (equivalent to the anterior cruciate ligament, or ACL, in humans) and the caudal cruciate ligament (equivalent to the posterior cruciate ligament in humans). Many people recognize the term ACL due to its association with sports injuries. These ligaments connect the femur and tibia in a diagonal pattern, forming an X shape—hence the name "cruciate." The cranial/anterior cruciate ligament plays a crucial role in stabilizing the knee by preventing the tibia from shifting forward beneath the femur. When it ruptures, the knee becomes unstable and begins to slip—see the video below. | A normal knee |
| How can I tell if my dog's knee is injured? A ruptured cruciate ligament is the most common knee injury in dogs. In fact, sudden hind leg lameness is often due to a torn cranial cruciate ligament rather than another cause. Many owners notice that their dog suddenly experiences severe pain, sometimes to the point of barely being able to bear weight on the affected leg. While the lameness may seem to improve after a week or two if left untreated, the knee will remain swollen, and arthritis will develop rapidly. The key to diagnosing a ruptured cruciate ligament is identifying an abnormal knee movement known as the "drawer sign." This movement does not occur in a healthy knee. The second video clip demonstrates this diagnostic test. | A knee with a complete rupture of the cranial cruciate ligament |
What Happens if the Cruciate Rupture is Not Surgically Repaired
Without an intact cruciate ligament, the knee becomes unstable, leading to abnormal wear on the bones and meniscal cartilage. Over time, the joint undergoes degenerative changes, with bone spurs (osteophytes) forming, causing chronic pain and reduced mobility. While surgery can help stabilize the joint and slow this progression, it cannot reverse the damage already done.
Without an intact cruciate ligament, the knee becomes unstable, leading to abnormal wear on the bones and meniscal cartilage. Over time, the joint undergoes degenerative changes, with bone spurs (osteophytes) forming, causing chronic pain and reduced mobility. While surgery can help stabilize the joint and slow this progression, it cannot reverse the damage already done.
- In some patients, osteophytes can begin forming as early as one to three weeks after a cruciate ligament rupture. While all dogs will eventually develop degenerative joint changes, large-breed dogs tend to struggle more with the condition. Initially, a dog may seem to improve after several weeks, but full, long-term recovery back to normal function without intervention is unlikely.
- A study followed a group of dogs for six months after a cruciate ligament rupture. By the end of the study, 85% of dogs weighing less than 15 kg had regained near-normal or improved function. In contrast, only 19% of dogs over 15 kg achieved similar recovery. Regardless of size, both groups required at least four months to reach their maximum level of improvement.
What Happens in Surgical Repair?
There are three different surgical repair techniques commonly used today.
Extracapsular Repair
This procedure is the traditional surgical approach for repairing a cruciate rupture. It involves creating an artificial ligament on the outside of the joint. While this was once the primary method of repair, it is now understood that, regardless of the material used, the artificial ligament begins to loosen within two months.
In this procedure, the first step is to open and inspect the knee joint—an essential part of any knee surgery. The torn or partially torn cruciate ligament is then removed, and any significant bone spurs are trimmed using a specialized instrument called a rongeur. If the meniscus is damaged, the affected portion is excised. To stabilize the joint, a strong suture is looped around the fabella behind the knee and threaded through a hole drilled in the front of the tibia. This tightens the joint, preventing the abnormal drawer motion and effectively taking over the function of the cruciate ligament.
There are three different surgical repair techniques commonly used today.
Extracapsular Repair
This procedure is the traditional surgical approach for repairing a cruciate rupture. It involves creating an artificial ligament on the outside of the joint. While this was once the primary method of repair, it is now understood that, regardless of the material used, the artificial ligament begins to loosen within two months.
In this procedure, the first step is to open and inspect the knee joint—an essential part of any knee surgery. The torn or partially torn cruciate ligament is then removed, and any significant bone spurs are trimmed using a specialized instrument called a rongeur. If the meniscus is damaged, the affected portion is excised. To stabilize the joint, a strong suture is looped around the fabella behind the knee and threaded through a hole drilled in the front of the tibia. This tightens the joint, preventing the abnormal drawer motion and effectively taking over the function of the cruciate ligament.
- After surgery, the dog may keep the leg lifted for about two weeks. However, knee usage gradually increases over the following two months, with most dogs eventually returning to normal function..
- After surgery, the dog typically requires 8 to 12 weeks of restricted exercise, including no running and only being taken outside on a leash, even in the backyard.
- The suture used in surgery will gradually loosen and break within 2 to 12 months, at which point the dog's own healed tissue will support the knee.
Tibial Plateau Leveling Osteotomy (TPLO)
This procedure takes a fresh approach to knee joint biomechanics and was initially designed for larger breed dogs. However, it is now recognized as the preferred surgical option for both large and small breeds. Compared to extracapsular repair and TTA, this is the only procedure that significantly slows the progression of arthritis in most dogs.
This procedure alters the angle at which the femur applies weight to the flat "plateau" of the tibia. By cutting and rotating the tibia, the dog's natural weight-bearing forces help stabilize the knee joint. As with other knee surgeries, the joint must be opened, and any damaged meniscus removed. The remnants of the cruciate ligament may be left intact or removed, depending on the extent of the damage.
This surgery is complex and requires specialized training in the technique. Multiple radiographs are needed to accurately calculate the osteotomy angle (the cut in the tibia). While this procedure is more invasive than extracapsular repair and typically more expensive, it offers significantly superior results.
Tibial Tuberosity Advancement (TTA)
The TTA (Tibial Tuberosity Advancement) procedure also utilizes knee biomechanics to enhance stability but does so by altering the angle of the patellar ligament. This is achieved by cutting and repositioning the tibial crest, where the patellar ligament attaches, and securing it with a titanium or steel "cage," "fork," and plate, along with bone grafts to maintain the new alignment. Like the TPLO, this procedure involves cutting bone and requires specialized equipment, including metal implant plates. Recovery is similar to that of the TPLO, but the TTA does not slow the progression of arthritis as effectively.
Which Procedure is Better?
The TTA and TPLO procedures are more invasive, costly, and require specialized equipment and trained personnel. They also carry a higher risk of complications. Are they worth it? Despite the differences in surgical approach, studies suggest that one-year post-operative outcomes are similar across all three procedures—extracapsular repair, TPLO, and TTA. However, arthritis progresses much more rapidly with the extracapsular technique and TTA compared to TPLO. In the long run, joint health is significantly better with TPLO, and some evidence suggests that dogs may return to normal function more quickly with this procedure.
This procedure takes a fresh approach to knee joint biomechanics and was initially designed for larger breed dogs. However, it is now recognized as the preferred surgical option for both large and small breeds. Compared to extracapsular repair and TTA, this is the only procedure that significantly slows the progression of arthritis in most dogs.
This procedure alters the angle at which the femur applies weight to the flat "plateau" of the tibia. By cutting and rotating the tibia, the dog's natural weight-bearing forces help stabilize the knee joint. As with other knee surgeries, the joint must be opened, and any damaged meniscus removed. The remnants of the cruciate ligament may be left intact or removed, depending on the extent of the damage.
This surgery is complex and requires specialized training in the technique. Multiple radiographs are needed to accurately calculate the osteotomy angle (the cut in the tibia). While this procedure is more invasive than extracapsular repair and typically more expensive, it offers significantly superior results.
- Most dogs typically begin touching their toes to the ground within 10 days after surgery, though in some cases, it may take up to three weeks.
- As with other surgical techniques, exercise must be restricted for 8 to 12 weeks.
- Most dogs regain full function within 3 to 4 months after surgery and can gradually return to normal activity.
- Athletic dogs experience the best outcomes with this surgery.
Tibial Tuberosity Advancement (TTA)
The TTA (Tibial Tuberosity Advancement) procedure also utilizes knee biomechanics to enhance stability but does so by altering the angle of the patellar ligament. This is achieved by cutting and repositioning the tibial crest, where the patellar ligament attaches, and securing it with a titanium or steel "cage," "fork," and plate, along with bone grafts to maintain the new alignment. Like the TPLO, this procedure involves cutting bone and requires specialized equipment, including metal implant plates. Recovery is similar to that of the TPLO, but the TTA does not slow the progression of arthritis as effectively.
Which Procedure is Better?
The TTA and TPLO procedures are more invasive, costly, and require specialized equipment and trained personnel. They also carry a higher risk of complications. Are they worth it? Despite the differences in surgical approach, studies suggest that one-year post-operative outcomes are similar across all three procedures—extracapsular repair, TPLO, and TTA. However, arthritis progresses much more rapidly with the extracapsular technique and TTA compared to TPLO. In the long run, joint health is significantly better with TPLO, and some evidence suggests that dogs may return to normal function more quickly with this procedure.
How is the TPLO performed?
| Before surgery, an X-ray of the stifle is taken to measure the tibial plateau angle, the slope at the top of the shin bone. The goal of the procedure is to reduce this angle, eliminating dynamic joint instability (cranial tibial thrust). This is typically achieved by adjusting the angle to between 4 and 10 degrees, similar to that of the human knee. Surgery usually begins with an examination of the inside of the stifle joint, either arthroscopically or through open joint surgery, to assess the meniscal cartilage for damage. Any damaged cartilage must be removed to restore normal, pain-free function. The TPLO procedure itself involves using a specialized curved saw blade to make a precise cut on the medial (inner) surface of the tibia. The cut portion is then rotated to achieve the desired tibial plateau angle. To stabilize the new alignment, a stainless steel bone plate is secured to the bone, ensuring proper healing and long-term joint stability. Now that you know a bit about TPLO, let’s review some questions about the procedure. |  |
Q: Does My Dog Really Need Surgery? I Read That They’ll Do Just Fine Without Surgery.
A: Published studies indicate that about 15% of dogs can regain reasonably good clinical function without surgery, with most of these cases being small breeds weighing under 7 to 10 kg. Dogs that do recover normal function typically do so within 4 to 6 weeks after the initial onset of lameness. However, for the majority of dogs, surgery is the only reliable way to restore proper function—braces, medications, herbs, physical therapy, or simply hoping for improvement are not effective alternatives.
Q: Which Patients Will Benefit From TPLO?
A: Although TPLO can be performed on almost any patient, including small dogs and cats, it is particularly beneficial for larger, active breeds. While opinions among surgeons may vary, most agree that smaller dogs tend to have similar outcomes regardless of the surgical technique used. In general, dogs weighing over 20 kg (45 pounds), especially those with high activity levels, experience the greatest benefits from TPLO.
Q: Why Is TPLO So Costly, Especially When Compared To Other Cruciate Repair Surgeries?
A: TPLO requires specialized equipment, including a motorized bone saw with a uniquely designed curved blade, a stainless steel bone plate, and 6 to 9 bone screws. The procedure also involves taking 4 to 6 X-rays and demands extensive training for the surgeon. Each surgery requires a significant time investment, with preparation, operation, and recovery taking approximately 2 to 4 hours per patient.
Q: What Aftercare Is Required?
A: Surgeons take different approaches to post-operative care, and there is no definitive evidence to determine the best method. Some recommend strict rest, limiting stair climbing, and kenneling when unsupervised. Others encourage controlled leash walks and moderate exercise, while some advocate for immediate post-surgical physical rehabilitation. Regardless of the approach, follow-up X-rays are necessary at various stages to monitor bone healing. Once the bone has fully healed, exercise can be gradually increased to normal levels.
Q: What About Possible Complications?
A: TPLO is a major surgical procedure, and complications can occur. Research suggests that complication rates may be slightly higher than with less invasive surgeries, though factors such as patient characteristics and surgeon experience also play a role. Most complications are minor and can be managed without additional surgery, leading to successful outcomes. These include issues like infections and patellar tendon inflammation.
More serious complications, such as plate or screw failure and fractures of the tibia or fibula, are uncommon. There have also been rare cases of bone cancer developing months or years after surgery in the operated area. However, the connection between TPLO and bone cancer remains controversial, as the upper tibia is a common site for this cancer in dogs, even in those without prior surgery or cruciate issues. Whether TPLO increases this risk is unclear.
One of the most frequent post-operative complications is not directly related to TPLO itself. Meniscal cartilage tears are a common consequence of an unstable joint and may be present at the time of surgery or develop later. Up to 11% of dogs experience new meniscal tears post-surgery, similar to rates seen in humans undergoing knee surgery. These dogs often recover well after surgery but may suddenly become lame again weeks or months later due to a meniscal tear.
Q: Is TPLO Really Better Than Other Surgical Options?
A: If your dog is large, young, and active, the answer is likely yes—TPLO is the best option. However, the supporting research has not always been conclusive. For the first 20 to 25 years after TPLO was developed, surgeons observed significantly better outcomes in large dogs compared to other surgical techniques. Yet, early research data didn’t seem to confirm these findings.One major factor was Dr. Barclay Slocum’s decision to patent the TPLO technique and equipment, which limited access to the procedure and subsequently restricted research opportunities. Additionally, veterinary research is inherently more limited in scope compared to human medicine. While studies in the New England Journal of Medicine often involve tens or even hundreds of thousands of human patients, veterinary studies are typically much smaller—considering a study with 50 animals to be substantial. The reason? Funding. The financial resources available for veterinary research are vastly smaller than those in human medicine.
In recent years, however, research has begun to validate what surgeons have long observed: dogs undergoing TPLO recover faster, develop less joint arthritis, and achieve better long-term function compared to other surgical techniques. Current evidence indicates that TPLO provides superior outcomes over TTA and extracapsular repair. While definitive conclusions are still being drawn, it appears that other similar procedures, such as CWO, CBLO, and TTO, may also offer similar benefits.
A: Published studies indicate that about 15% of dogs can regain reasonably good clinical function without surgery, with most of these cases being small breeds weighing under 7 to 10 kg. Dogs that do recover normal function typically do so within 4 to 6 weeks after the initial onset of lameness. However, for the majority of dogs, surgery is the only reliable way to restore proper function—braces, medications, herbs, physical therapy, or simply hoping for improvement are not effective alternatives.
Q: Which Patients Will Benefit From TPLO?
A: Although TPLO can be performed on almost any patient, including small dogs and cats, it is particularly beneficial for larger, active breeds. While opinions among surgeons may vary, most agree that smaller dogs tend to have similar outcomes regardless of the surgical technique used. In general, dogs weighing over 20 kg (45 pounds), especially those with high activity levels, experience the greatest benefits from TPLO.
Q: Why Is TPLO So Costly, Especially When Compared To Other Cruciate Repair Surgeries?
A: TPLO requires specialized equipment, including a motorized bone saw with a uniquely designed curved blade, a stainless steel bone plate, and 6 to 9 bone screws. The procedure also involves taking 4 to 6 X-rays and demands extensive training for the surgeon. Each surgery requires a significant time investment, with preparation, operation, and recovery taking approximately 2 to 4 hours per patient.
Q: What Aftercare Is Required?
A: Surgeons take different approaches to post-operative care, and there is no definitive evidence to determine the best method. Some recommend strict rest, limiting stair climbing, and kenneling when unsupervised. Others encourage controlled leash walks and moderate exercise, while some advocate for immediate post-surgical physical rehabilitation. Regardless of the approach, follow-up X-rays are necessary at various stages to monitor bone healing. Once the bone has fully healed, exercise can be gradually increased to normal levels.
Q: What About Possible Complications?
A: TPLO is a major surgical procedure, and complications can occur. Research suggests that complication rates may be slightly higher than with less invasive surgeries, though factors such as patient characteristics and surgeon experience also play a role. Most complications are minor and can be managed without additional surgery, leading to successful outcomes. These include issues like infections and patellar tendon inflammation.
More serious complications, such as plate or screw failure and fractures of the tibia or fibula, are uncommon. There have also been rare cases of bone cancer developing months or years after surgery in the operated area. However, the connection between TPLO and bone cancer remains controversial, as the upper tibia is a common site for this cancer in dogs, even in those without prior surgery or cruciate issues. Whether TPLO increases this risk is unclear.
One of the most frequent post-operative complications is not directly related to TPLO itself. Meniscal cartilage tears are a common consequence of an unstable joint and may be present at the time of surgery or develop later. Up to 11% of dogs experience new meniscal tears post-surgery, similar to rates seen in humans undergoing knee surgery. These dogs often recover well after surgery but may suddenly become lame again weeks or months later due to a meniscal tear.
Q: Is TPLO Really Better Than Other Surgical Options?
A: If your dog is large, young, and active, the answer is likely yes—TPLO is the best option. However, the supporting research has not always been conclusive. For the first 20 to 25 years after TPLO was developed, surgeons observed significantly better outcomes in large dogs compared to other surgical techniques. Yet, early research data didn’t seem to confirm these findings.One major factor was Dr. Barclay Slocum’s decision to patent the TPLO technique and equipment, which limited access to the procedure and subsequently restricted research opportunities. Additionally, veterinary research is inherently more limited in scope compared to human medicine. While studies in the New England Journal of Medicine often involve tens or even hundreds of thousands of human patients, veterinary studies are typically much smaller—considering a study with 50 animals to be substantial. The reason? Funding. The financial resources available for veterinary research are vastly smaller than those in human medicine.
In recent years, however, research has begun to validate what surgeons have long observed: dogs undergoing TPLO recover faster, develop less joint arthritis, and achieve better long-term function compared to other surgical techniques. Current evidence indicates that TPLO provides superior outcomes over TTA and extracapsular repair. While definitive conclusions are still being drawn, it appears that other similar procedures, such as CWO, CBLO, and TTO, may also offer similar benefits.
Updated 27/12/2019
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