Canine Cruciate Ligament Rupture

What is the cruciate ligament?

There are actually two cruciate ligaments. The anterior and posterior cruciate ligaments provide stability to the knee. The knee joint is one of the weakest in the dogs body. Just as athletes frequently suffer knee injuries, so can dogs.

How can my dog injure its cruciate ligament?

The knee joint is relatively unstable because there are no interlocking bones. Two bones, the femur (thigh bone) and the tibia (shin bone) are joined by several ligaments. Sudden, excessive twisting or shearing forces on the knee may tear the anterior cruciate ligament. When the ligament is torn, the knee joint becomes unstable and the dog can not bear weight on that limb without considerable pain. Many dogs also tear a cartilage in the knee called the meniscus when the ligament tears.

How do I know if my dog has a torn cruciate ligament?

Diagnosing a torn cruciate ligament needs to be done by your veterinarian. Your veterinarian will first observe the way your dog walks. Next the veterinarian will manipulate the knee to detect any instability. The instability is called a drawer sign because the tibia and femur slide over each other like a drawer. Sometimes the dog will need to be anesthetized to allow the veterinarian to do these manipulations.

Can a torn cruciate ligament be treated?

Yes, the treatment requires surgery. First, the veterinary technician anesthetizes the dog and prepares the knee for sterile surgery. The veterinary surgeon opens the knee joint to remove the pieces of the torn ligament. The surgeon also inspects the cartilaginous meniscus for damage. If the damage is significant the meniscus is removed. The joint capsule is closed and a stabilization procedure is done to eliminate the drawer motion. There are many different techniques that may be used to stabilize the knee. Each surgeon has their own preferred method. If surgery is not performed as soon as possible after the ligament is torn, arthritic changes will occur that cannot be corrected, even with surgery.

What happens if a torn cruciate ligament is not treated?

If the dog weighs less than twenty pounds it may not have to have surgery to be able to walk again. There will probably be some permanent damage though. Dogs over twenty pounds will most likely develop severe arthritic changes that will cause pain for the rest of its life. Your veterinarian can advise you as to the best treatment for your pet.

by William M. Fraser, D.V.M.

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