Anterior Cruciate Ligament Injuries in Dogs by Frank Utchen, DVM

So you think you’re the only one suffering from “weekend warrior” syndrome? That’s the classic case of the middle-aged athlete who exercises only on the weekends and pays the price with little (or big) injuries that wouldn’t have happened 15 or 20 year ago.  Well, your dog is no different, and the high incidence of knee ligament injuries in dogs is testament to that reality.  In fact, knee ligament injuries are the most common orthopedic problem in dogs, and this week’s column will explain why this is and how it is fixed.  In dogs, as opposed to people, the femur (thigh bone) and tibia (shin bone) meet at a slight angle. Every time a dog takes a step the femur tends to slide backward slightly on the top of the tibia. This natural tendency is counteracted by the presence of a ligament in the joint called the Anterior Cruciate Ligament. You may know this as the “ACL” that so many people injure.  However, due to this continual stress on the knee, over time the ACL can weaken and either partially or completely tear. Of course, this kind of ligament injury can happen all at once without gradually wearing out in the first place. But the fact is that many dogs will demonstrate intermittent limping that seems to spontaneously fix itself, and only after months of this problem coming and going does the ligament finally give way and rupture completely. At that point, a dog will hold their leg up completely during each step, or will just barely use it.  When the ligament is partially or completely torn, the knee joint becomes severely unstable. This results in excess motion of the knee with each step and can lead to torn cartilage inside the knee as well.   So how is this problem fixed? Because a torn ligament will not heal, the surgeon has to rely on other techniques to return stability to the joint. There are two common procedures performed by veterinarians.   The first involves replacing the ligament with a heavy duty nylon material. Many veterinarians perform this procedure routinely to stabilize a knee joint with a torn ligament. It is referred to as the “Lateral Suture” technique.

The second procedure is more ingenious and involves re-configuring the knee joint by actually cutting the tibia with a high-speed orthopedic saw, then rotating the top portion forward slightly, and applying a bone plate and screws to hold the top of the tibia in its new orientation while the bone heals back together. By changing the angle that the femur and the tibia contact each other in the knee joint this procedure prevents the original tendency of the femur to slide backwards when the leg is stepped on, and eliminates the need for the ligament in the first place. This procedure is done almost exclusively by board-certified veterinary surgeons, and is called (ahem) a Tibial Plateau Leveling Osteotomy, or TPLO for short.  Each procedure has its advantages, but in the long run the key thing to help a dog return to full activity on their leg is the diligent post-operative use of physical therapy.  “Physical therapy for dogs?” you ask? Absolutely. Physical therapy can be as simple as passively extending and flexing your dog’s knee while they are lying on their side, or can be as involved as assisted swimming and special exercise programs designed by veterinarians and physical therapists. In the Bay Area there are several veterinary physical therapy facilities that can help dogs get back on their paws quickly.   Generally, by two months after knee surgery most dogs are walking very well on their previously injured leg, and by four months post-op they are fully recovered. In each case it is important to follow your veterinarian’s recommendations and not over-do the exercise by exercising too strenuously too soon.   Long term, any joint that has required surgery will probably have a greater than average chance of developing some arthritis in the future. The use of anti-inflammatory painkillers from time to time, and other joint supplements, may still be needed. But with proper surgery done as soon as possible after the ligament injury occurs, the risk of this long term effect can be minimized, and your dog should be able to return to the fully active lifestyle he or she was accustomed to before the injury occurred.