Cranial Cruciate Ligament Injury in Dogs

Laurie Anne Walden, DVM

Photo by Grant Durr on Unsplash

Injury of the cranial cruciate ligament in the knee is a common cause of hind limb lameness in dogs. Surgery is often the best treatment option.
 
The cranial cruciate ligament is one of the main structures that stabilizes the knee joint. This ligament is called the anterior cruciate ligament in humans. In humans, injury to this ligament is usually caused by trauma, especially while playing sports. In dogs, cranial cruciate ligament injury is more often caused by long-term, gradual degeneration that results in a partial or full ligament tear.
 
Some of the factors involved in cranial cruciate ligament degeneration in dogs are age, knee conformation, genetics, and body weight. Because these factors affect both knees, many dogs with a ligament tear in one knee develop the same problem in the other knee within a year or two.
 
Many dogs with cranial cruciate ligament injury also have a torn meniscus in the knee. The meniscus is a cartilage pad that provides cushioning between the femur (upper leg bone) and tibia (lower leg bone). A torn meniscus is painful. A meniscal tear can happen at the same time as the injury to the cranial cruciate ligament or much later as a result of knee instability.
 
Cranial cruciate ligament injury causes knee arthritis. The rate of progression of the arthritis partly depends on how the cruciate ligament injury is treated (with surgery or with medical management alone), meaning how soon the knee joint is stabilized.
 
Signs
A sudden full tear of the cranial cruciate ligament causes significant lameness; dogs are often unable to bear any weight on the affected leg. The signs of partial ligament tears and chronic ligament degeneration are less obvious. In these cases the lameness might improve with rest but doesn’t entirely disappear. Meniscal tears can cause a clicking sound in the knee joint. Arthritis resulting from chronic cruciate ligament injury eventually causes thickening of the knee joint.
 
Diagnosis
Full cranial cruciate ligament tears can often be diagnosed during a physical examination with tests that reveal instability in the knee joint. However, dogs are sometimes too tense (because of knee pain) for these tests. X-ray images sometimes show evidence of cruciate ligament rupture and can also help rule out other possible causes of the lameness. Partial tears and meniscal tears are harder to diagnose and are typically found with advanced imaging techniques or seen during knee surgery.
 
Treatment
Cranial cruciate ligament injury is treated either surgically or with medical management alone. The choice of treatment for an individual dog depends on the type of injury; the dog’s size, age, activity level, and state of health; and the owner’s preferences and financial resources. For dogs with a complete ligament tear, surgical treatment followed by physical rehabilitation usually yields the best functional result.
 
A number of surgical options are available and are typically performed by a veterinary surgery specialist. The torn ligament can’t actually be repaired, so the goals of surgery are to stabilize the joint and remove damaged (painful) parts of the meniscus. Some surgical techniques change the biomechanics of the knee joint by cutting into the tibia to adjust the way the large leg muscles attach to the front of the knee. Other techniques use suture material to mimic the function of the cranial cruciate ligament. All surgical options require strict exercise restriction for several weeks to a few months after the procedure.
 
Medical management involves exercise restriction and anti-inflammatory medication. Physical rehabilitation and custom orthotics, or knee braces, might help some dogs. Weight management is crucial for overweight dogs with knee ligament injuries.
 
For more information about treatment options, see the American College of Veterinary Surgeons website: https://www.acvs.org/small-animal/cranial-cruciate-ligament-disease/
 
Image source: https://unsplash.com/photos/yellow-labrador-retriever-puppy-lying-on-white-textile-biW4WcdmZyA

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