Cruciate Ligament Injury

The weather has finally gotten warm enough for the Bakers to shake off some cabin fever outside with their rowdy two year old Labrador Retriever “Riley‘. As Riley was jumping back into the vehicle after a day of running in the mountains she missed the tailgate of the vehicle with her back feet and fell to the ground with a yelp. She held up a hind leg and hobbled around until she got hoisted into the back by her owners. They drove home, not too worried that anything serious had happened, after all she had experienced several incidents like this in the past and had always been fine after a few days of rest. Three days later, however, she was still not wanting to use that hind leg and that is how she found herself in my office.

We located the source of pain in her stifle, which is the joint on the hind leg that corresponds with a person’s knee. On physical exam there was a palpable instability in the stifle that indicated a torn cruciate ligament in the joint. X-rays do not show the ligament itself, but they do show fluid accumulation in the joint that happens as a result of such a tear, and in Riley’s case they also showed a significant amount of arthritis that suggested that she had suffered smaller injuries to her cruciate ligament in the past that had caused low grade instability in her stifle for a while. Although this incident seemed like an isolated episode she had probably been periodically snapping a few fibers in her crucuate ligament and then recovering quickly, but this time that weakened ligament was ready to tear completely when she fell.

The cruciate ligaments are a pair of ligaments in the stifle that attach between the femur, the upper thigh bone, and the tibia, the shin bone, and keep the joint stable. Extreme force applied to the stifle tends to cause the cranial cruciate ligament (called the anterior cruciate in people) to rupture. This allows the bones of the stifle joint to rock back and forth and grind against each other with every step, causing pain and arthritis. People, especially athletes like football players, suffer this kind of injury very frequently as well.

In small dogs, dogs under 45 pounds, and the occasional cat or ferret that suffers this sort of injury, the scar tissue that forms around the joint will often stabilize the stifle enough for good recovery without surgical interference. In dogs over 45 pounds their weight tends to overwhelm the ability of scar tissue to stabilize the stifle and untreated cranial cruciate injuries often lead to debilitating arthritis over time.

Surgical stabilization of the stifle joint in big dogs is usually the recommended treatment. There have been a multitude of stifle repair procedures developed over time and there is always hot debate about which procedure is the best. Currently the most commonly performed procedures are done at an orthopedic specialist’s practice because they require specialized equipment, like endoscopes, and training. There are recent studies out that suggest that some of the older repair techniques that were commonly performed by general practitioners may have equally good outcomes as the newer surgeries.

In some dogs the shape of their legs is a predisposing factor for cruciate injuries, and in those cases it is not unusual that the dog injures the other leg in the same way. Some dogs have injured both stifles and have incredible difficulty using their hind legs. Those dogs often look like they have hip pain, but x-rays can help show if the problem is really in the hips or in the stifles. Surgical repair often results in significant improvement, even when the problem is very longstanding.