Article by: Dr Claudia Meyers, DVM
A Breed Apart Animal Hospital
202 South Gammon Road
Madison, WI 53717

Anterior Cruciate Ligament Rupture

The stifle, or knee joint, is a complex combination of bones, muscles, tendons, cartilage and ligaments. They all work together to help that joint be able to flex and extend comfortably. The anterior and posterior cruciate ligaments cross in the middle of the knee joint. They each run from the femur, the upper bone of the knee, to the tibia, the lower bone of the knee. Together they help keep these bones from slipping back and forth. A common injury in both dogs and people is the rupture of the anterior cruciate ligament. In dogs, this happens most commonly in the ball chasing, Frisbee catching type dogs, especially when they jump up in the air and land on those hind legs. It can happen any time a dog runs off a deck or steps in a hole and the lower part of his leg stays in one place and the upper part goes in a different direction. When the anterior cruciate ligament if completely ruptured, the knee joint is very unstable. What we will notice usually is that the dog will all of a sudden hold his leg up and not use it. Sometimes the episode that caused the injury will be obvious; running, jumping, leaping. Other times it may be more subtle, with the knee just getting twisted the wrong way. After a rupture, most times we can feel what is called a drawer sign when feeling the knee. This is when we can move the tibia forward with respect to the femur. In some very large, strong dogs we may have to sedate them to be able to feel this motion.

If left unattended after a cruciate ligament rupture, the stifle will try to heal itself. Over time, connective tissue will form around the knee, with a rubber band or ace bandage type of affect. This does stabilize the joint to some extent and some dogs will be able to use the leg fairly well after a few weeks. In cats and small dogs under about twenty pounds, many times all they need is rest and time and they will do well with the knee. In larger dogs, where their weight and activity put more stress on the joint, the knee rarely can stabilize itself well enough for them to have a comfortable joint. The ligament itself cannot reform and without this, the motion in the knee will never be normal. Over time arthritis will form in that joint and will cause problems. We can surgically stabilize the stifle after a cruciate ligament rupture and this approach is usually recommended for large, young dogs. If a large dog is over 10 or 12 years old, you may want to avoid putting him through a major surgery. If he can use the leg well after a few weeks, surgery may not be as necessary for him as a younger dog. With the surgery, we try to reconstruct the support that the anterior cruciate ligament used to give to the knee and therefore bring the motion in the knee back closer to normal. This will make the knee stronger and more comfortable and hopefully decrease arthritis formation in the future. In older dogs, arthritis may form in that knee with or without surgery just because of normal aging. If an older dog is still very active or he cannot use the leg well with rest and time, surgery may still be the answer for him.

There are many surgical ways to repair an anterior cruciate ligament. The knee joint should always be opened and examined for any other injury. Commonly, the medial meniscus will be torn at the same time as the ligament if ruptured. The medial meniscus is a cushion of cartilage between the tibia and femur. If it is injured, the torn portion should be removed. The remaining tags of the ruptured ligament should also be removed during surgery. Finally, some procedure to reconstruct or mimic the stabilizing force of the anterior cruciate ligament should be done. Most dogs do very well after surgery, starting to use the leg 4-6 weeks following the procedure.

What can we do to limit the frequency of these injuries? If we didn’t let our dogs run or jump and never threw a ball or Frisbee to them, these injuries would happen a lot less commonly, but that wouldn’t be any fun for us or them. What we might want to do is to keep our dogs from being overweight. That would help decrease the stress from extra weight on the knee. If we exercise our dogs regularly, we can keep their muscles strong and this will help stabilize the joint. Swimming is a great non-traumatic exercise, as is walking. Playing on level ground will help decrease the chance our dog will step down into a hole or twist his knee. With icy weather, we should check for slippery surfaces before we throw our Frisbees or balls.

If you have any questions, please contact us at: 608-225-1559 or barknwag@charter.net

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