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The knee is prone to a number of injuries. One of the most common knee injury in dogs is a ruptured cruciate ligament. Large breed dogs such as Rottweilers or the very excitable ones such as Border Collies do suffer commonly from that disease and it is the topic for today's discussion.

The knee anatomy

To understand what a cruciate injury is, it is important to know how the knee joint is built.

The knee is a joint that is formed by three bones: femur, patella and tibia.

Two ligaments cross into the knee joint itself. They are called the cruciate ligaments. The one towards the front of the leg is called the anterior cruciate ligament and the one crossing behind it, is called the posterior cruciate ligament.

The ligament that suffers most injuries is the anterior cruciate ligament. When the ligament ruptures, the joint becomes unstable. The femur and tibia can move back and forth across each other. This is called a “drawer sign”.

What are the symptoms of a cruciate ligament injury?

Lameness in the hind leg is the most common sign of cruciate ligament injury. The animal may be unable to bear its weight or may limp. The lameness occurs immediately after the injury and may subside after several weeks but is likely to return.

Other symptoms of cruciate ligament injury include:

• Hind leg extended when sitting
• Pain when knee joint is manipulated
• Resistance to exercise
• Stiffness after exercise
• Swelling of the knee
• Weight shifted to one side of body when standing
• If the meniscus is torn, a pop/snap may be heard when the animal walks

How is a ruptured cruciate ligament diagnosed?

The diagnosis of a ruptured cruciate ligament is made through observing abnormal movement of the joint. On occasion, this can be done in consultation if the patient is relaxed enough. However on many occasion, this is better evaluated on a sedated patient.

The veterinarian will try to demonstrate a “drawer sign” movement in the knee joint: the veterinarian places one hand around the femur and one around the tibia in a precise manner. By applying pressure on the knee, the veterinarian will feel the bones move abnormally in what is called a “drawer sign”. It is called that because the movement of the femur in relation to the tibia is similar to pulling and pushing the drawer of a cabinet.

It is important to note that this “drawer sign” is the only way to make a diagnosis of a cruciate injury. However, you will find that the vet will also be taking some radiographs. Those are taken to evaluate secondary arthritic changes in the knee joint which will influence the potential for perfect recovery following treatment.

The treatment for a cruciate injury is complex and this will be dealt with in another episode.

Posted by Vetstoria.com, 7 months ago