Craniomedial and caudolateral ligamentous bundles compose the cranial cruciate ligament, which originates on the caudomedial aspect of the lateral femoral condyle and inserts centrally on the tibial plateau caudal to the cranial intermeniscal ligament—says Chapter 16 of the Orthopedic Disorders of the Stifle, in Saunders Manual of Small Animal Practice.
“Wwwhhhaaaaatttt?” as my friend, Kirby, would say. The above excerpt is simply a $98,000 veterinary college tuition definition of your dog’s front or cranial cruciate ligament (CCL), like your anterior cruciate ligament or ACL. Indeed, what a horrible flashback to vet school! Well, unfortunately, busting, tearing or rupturing the CCL is one of the more common orthopedic injuries to your dog’s knees (stifles). In last month’s issue of Clinician’s Brief, I read that five out of 100 dogs will suffer from this injury. In fact, my patient ‘Chewie’ was the latest victim of such an injury and that prompted me to discuss this all too common knee malady. And I will try to do it in a digestible form, unlike that which we had to choke down decades ago.
The cruciate ligaments help stabilize the stifle joint. Cruciate stands for cross, and accurately describes the front cruciate ligament making an ‘X’ with the back cruciate ligament. They are located, essentially, inside the knee joint—joined by other ligaments, tendons, bone processes and other helpful stabilizers—to keep this joint held together. The front (cranial) cruciate ligament goes from the back outside part of the bottom of the thigh (femur) bone. It then attaches to the ridge on top of the shin bone (called the tibial plateau). The back (caudal) cruciate ligament originates on the back inside of the bottom of the femur and goes to the back outside of the tibial plateau. Thus, the cross, the X, of the cruciate ligaments have formed.
The job of the cruciate ligaments is to keep the knee, or stifle, stable. They stop hyperextension of the joint, keeping the tibia in its rightful position. So now that we know what they are, how they are positioned, and how they work, what possibly could go wrong?
Like I said, a lot. It seems to be more often the cranial cruciate ligament that ruptures. There are two kinds of ligament ruptures: One, it just snaps under intense pressure; and two, minor, microscopic and repetitive damage to the ligament causes it to weaken and then ultimately give way. Other factors are at play here, as well, like what breed of dog you have and how its hind legs are conformed, how fat your dog is and even some autoimmune diseases.
The injury usually occurs when exercising. For example, the dog may be running then change directions: The leg gets a little straighter than anticipated, the paw hits the ground and the shin bone moves too far forward on the thigh bone…and pop! goes the weasel. Sometimes there will be a partial tear that shows up with all the pain and symptoms of lameness, but is far more difficult to diagnose.
Symptoms are that of lameness: The dog may be non-weight bearing in that limb right after the injury occurs, then proceed to partial weight bearing with a noticeable limp. Most of the time, the dog will tap that paw on the ground gingerly when standing at rest. Gradually, there will be muscle loss in that leg from disuse. This injury hurts, and no, your dog will likely not cry about it. The fact that your pet is limping is because it hurts not to.
What’s the cure? Surgery really is the only viable repair. Unlike bones, ligaments don’t find their other broken ends and reunite. You’ll need an orthopedist to facilitate their reunion. Your veterinarian will advise you of your prognosis and postoperative chores. One of the hardest parts of fixing ruptured cranial cruciate ligaments is keeping the dog from wrecking the great job the surgeon did after you spent all that money! So, keep your dogs skinny and off the slopes. As for Chewie, all is going well and according to plan. He’ll be chasing bunnies in no time!
Dr. Kenneth Geoghegan, of Village Veterinary Hospital in Warson Woods (villagevethosp.com), has been a neighborhood veterinarian since 1992.