Cranial cruciate ligament tears and TPLO surgery

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Tibial plateau leveling osteotomy (TPLO) surgery is a procedure used to help dogs and cats regain mobility following a tear of the cranial cruciate ligament (CCL). The CCL is the canine and feline equivalent of the anterior cruciate ligament (ACL) in humans and connects the femur to the tibia. If the CCL tears, the tibia can slide forward relative to the femur, leading to instability in the stifle joint.¹

In dogs, the majority of cruciate tears are a result of degeneration, obesity, poor physical condition, conformation, and breed.² These canines commonly experience partial CCL tearing that, over time, progresses to a full tear.² In cats however, degenerative disease is rarely the culprit of CCL ruptures, although it can occur in felines that are overweight. Instead, CCL tears in cats are most frequently caused by trauma.³

The top of the shin bone in dogs has a natural slope, making the bones in the leg more susceptible to sliding, according to a Texas A&M University College of Veterinary Medicine and Biomedical Sciences (VMBS) report.¹ “Without the CCL holding the bones in place, that slope causes instability that leads to pain, inflammation, and the development of arthritis over time,” Katherine Barnes, DVM, MS, DACVS (Small Animal), clinical associate professor at VMBS, said in the report.¹

Although any feline or canine patient can tear their CCL, it is most common in large, active dogs. At least half of canine patients who experience a CCL tear in one knee will likely develop a similar issue in the other knee.⁴ Breeds most at-risk for a CCL tear include⁴:

• Akitas
• Chesapeake Bay retrievers
• Labrador retrievers
• Mastiffs
• Newfoundlands
• Rottweilers
• Saint Bernards
• Staffordshire terriers
• West Highland white terriers

To treat CCL tears, patients may undergo TPLO surgery. The procedure involves reshaping the knee by making a circular cut in the tibial plateau. The cut section is then rotated to reduce the slope of the tibial plateau until it reaches a more level orientation that brings the tibial plateau to approximately 90 degrees to the attachment of the quadriceps muscles, helping to prevent the abnormal forward sliding of the tibia that occurs with a CCL tear.^1,2

“Instead of replacing or repairing the damaged ligament, TPLO changes the anatomy of the knee to eliminate the need for the ligament entirely,” Barnes said in the Texas A&M report.¹ “This is done by making a curved cut in the top of the tibia to flatten its weight-bearing surface. The bone is then secured with a specialized bone plate and screws.”

“Clipping the fur and scrubbing the leg beforehand is a critical step, as it helps decrease the risk of postoperative infection,” Barnes continued.¹ “Before surgery, X-rays are performed to confirm the diagnosis and rule out any other sources of pain, such as from a fracture, and blood work is done to ensure the patient is healthy for anesthesia. X-rays are also taken after surgery to ensure that the implants are well-positioned before waking the patient up.”

According to VMBS, the entire process, from preparation to waking the patient, generally takes a few hours and has “excellent” outcomes.¹ Still, for safe healing, carefully guiding clients through the recovery process is a crucial step.

References

1. When the knee gives out: Understanding TPLO surgery. News release. Texas A&M University Veterinary Medicine & Biomedical Sciences. May 29, 2025. Accessed June 2, 2025. https://vetmed.tamu.edu/news/pet-talk/understanding-tplo-surgery/
2. Canine cruciate ligament injury. Colorado State University James L. Voss Veterinary Teaching Hospital. Accessed June 2, 2025. https://vetmedbiosci.colostate.edu/vth/services/orthopedic-medicine/canine-cruciate-ligament-injury/
3. Cranial cruciate ligament injury disease (feline). Manchester Veterinary Specialists. Accessed June 2, 2025. https://www.mvsvets.co.uk/pet-owners/cranial-cruciate-ligament-disease-feline/#:~:text=What%20causes%20cruciate%20ligament%20disease,is%20often%20in%20overweight%20cats.
4. Cranial cruciate ligament injury disease (CCL) in dogs. Schwarzman Animal Medical Center. March 21, 2024. Accessed June 2, 2025. https://www.amcny.org/pet_health_library/cranial-cruciate-ligament-disease-in-dogs/