By Christie Long
Who among us does not shudder quietly as the ski patrol packs away an unlucky soul into the gurney to be hauled down from the mountain, and wonder what malady took down one of our fellow snow-lovers?
Dogs and people share very similar anatomy at the knee joint, and when you learn a little bit about how its put together it’s hard to understand how it works at all. One of the most common orthopedic injuries in people, the torn anterior cruciate ligament (ACL) is also very common in our canine friends.
The knee joint consists of the femur, or thigh bone, the tibia, also called the skin bone, and a collection of tendons, ligaments, and other small bones that hold it all together in a fashion not unlike the chewing gum and bailing wire model.
In dogs we see a sudden onset of lameness and pain in one of the hind legs, and it usually occurs during strenuous exercise, like a game of fetch. The cranial cruciate ligament (CCL), which attaches to the front part of the tibia and the back part of the femur, controls and limits forward movement of the tibia relative to the femur, just like the ACL does in people.
Traumatic injury can cause a full or partial tear of this ligament, and profound pain and lameness that occurs in the acute phase will mellow after several days to mild to moderate discomfort. But the problem remains, and without intervention this injury causes lifelong pain and arthritis.
If your veterinarian suspects that your dog has an injury to its CCL, he will likely look for instability in the joint. X-rays are also important in making the diagnosis and ruling out other causes of lameness, like bone cancer.
A ligamentous injury to the knee almost always requires surgical correction, and even if the patient can be made comfortable with pain relief, the instability that results leads to the development of severe arthritis.
There have been several methods described for repairing a torn CCL in dogs. Interestingly, the main method for fixing this knee injury in people, which involves “transplanting" a ligament from a cadaver into the joint, does not work well in dogs. Sometimes very strong fishing line is looped behind and in front of the knee to simulate the presence of the CCL.
This technique has limitations, especially in large breed dogs (who, coincidentally, seem to be the ones that most commonly rupture their CCL). The other main technique, the TPLO, or tibial plateau-leveling osteotomy, actually changes the biomechanics of the knee, making it virtually impossible for the tibia to slip forward. The TPLO is generally thought of as the preferred treatment for a CCL tear.
As with any surgical procedure, dogs need pain relief and rest afterwards. They also benefit from physical therapy to build muscle and speed return to full function. Unfortunately, dogs who rupture one CCL are very likely to rupture the other within one year.
Christie Long is a veterinarian at the VCA Animal Hospital in Fort Collins, CO. Long left her job in software sales in 2000 to travel for 13 months. Along the way, she was touched by the plight of the animals she saw and somewhere in the Nepalese Himalayas she vowed to return to school to become a veterinarian. While she often finds end-of-life situations heart-wrenching, she considers herself blessed to be called upon as a trusted advisor to families during difficult times. Dr. Long’s family includes her husband and travel partner, Wiley, their 5-year-old son, Wiley IV, their dogs Pancake and Gizmo and cats Sneaky and Sidh.