Dog Cruciate Ligament Injuries

The most common orthopedic condition in dogs that veterinarians see if cruciate ligament injury. This disease can affect all breeds, genders, and ages of dogs. The disease has an extremely high economic impact on pet owners. A study was performed in 2005 looking at the estimated economic impact of this disease for the year of 2003 and the results showed that pet owners spent $1.32 billion (JAVMA, 2005) on the cost of treating dogs with cruciate ligament injuries. Unfortunately, the cost of treatment has only gone up from 2003.

The cranial cruciate ligament in the dog is similar to the anterior cruciate ligament in a person and performs many of the same functions within the dog knee. The cruciate ligaments (cranial and caudal in the dog and anterior and posterior in a person) are named because they form a cross or "X" within the knee. They are named by where they originate on the tibia, with the cranial or anterior cruciate ligament originating on the front of the tibia and inserting on the back of the femur. The cranial cruciate ligament's function is to prevent forward or cranial slipping or translation of the tibia compared to the femur and to stop excessive internal rotation and hyperextension of the knee.

In people, damaging the cruciate ligament requires some form of trauma to the knee such as getting hit in the knee like a football player, or falling and twisting the knee abnormally like skiers. Dogs can tear their cranial cruciate ligament in a similar way but can also injure it from normal, everyday activities like walking and running, without significant trauma. There are theories that the slant or angle of the top surface of the tibia where it comes in contact with the femur is to blame for this type of degenerative injury in the dog. Instead of all of a sudden coming up lame on the leg after running and falling, these dogs present with a slowly progressive lameness that can occur over months to a few years. Unfortunately, because degeneration of the ligament over time is usually the cause, it is very common that both knees have the same problem and often dogs tear the cranial cruciate ligament in the second knee within 1-2 years.

The first signs that an owner will see that their dog may have a cruciate ligament tear is lameness on the affected hind leg. This lameness can be all of a sudden while playing, or can be a slowly progressive lameness over time. When the lameness is slowly progressive, the dogs will often show a worsening of the lameness with exercise or after a prolong rest.

The diagnosis of a cranial cruciate ligament injury can be made by your veterinarian palpating your dog's knee. There are two tests that can be done to feel for abnormal sliding of the femur and tibia called the cranial drawer test and the cranial tibial thrust test. If abnormal movement is felt, then you can be comfortable saying that the cranial cruciate ligament is torn. In cases where the ligament is not completely torn, movement may be subtle and then further testing such as radiographs to show abnormal swelling or arthritis can be performed to help make the diagnosis.

Making the definitive diagnosis of a cruciate ligament tear is done by visually inspecting the ligament during surgery. This can be done by opening the joint to look at the ligament (arthrotomy) or by using a camera on the end of a scope (arthroscopy) to see within the joint. Many factors such as size of the dog, age of the dog, activity level of the dog, financial limitations of the owner, and surgeon's preference are all factors that determine what the best course of treatment is for each dog.