Cruciate Ligament Rupture

I know that knee injuries are common in people. Do they occur in dogs?

Just as football players frequently suffer knee injuries, the dog may also be prone to knee injuries since the knee joint is one of the weakest in the body.


Why is the knee so likely to be injured?

The knee joint is relatively unstable because there are no interlocking bones in the joint. Instead, the two main bones, the femur and tibia, are joined with several ligaments. When severe twisting of the joint occurs, the most common injury is a rupture of the anterior cruciate ligament which is one of two ligaments which actually cross over within the joint and ensure that it is stable and works in one plane. When it is torn, an instability occurs that allows the bones to move in an abnormal fashion in relation to each other. It is not possible to bear weight on the leg without it becoming unstable.


How is it diagnosed?

One of the most reliable means of diagnosing this injury is to move the femur and tibia in a certain way to demonstrate the instability. This movement is called a “drawer sign”. It can usually be demonstrated with the dog conscious. However, If there is severe pain, the dog has very strong leg muscles, or is uncooperative, it may be necessary to use a sedative or a light anaesthetic in order that the veterinary surgeon may examine the joint thoroughly it is also likely that radiographs will be taken to asses the joint.


How is it treated?

Correction of this problem requires surgery. A skilled surgeon can perform surgery and it is common practice to perform either a TTA or TPLO these are surgeries that focus on altering the level of the tibia and changing how this surface bears weight. 

Any surgery is aimed at improving function and reducing long term damage – in this case reduction in arthritis formation.


I have heard of torn cartilage. Does this also occur?

Occasionally the injury that causes a ruptured anterior cruciate ligament will also result in tearing of one or both of the menisci or “cartilages”. At the time of surgery, these are examined and treated, if necessary.


What happens if surgery is not performed?

Occasionally, the dog that has a ruptured cruciate ligament will become sound (will no longer limp) even if surgery is not performed. However, arthritis will usually begin and result in lameness a few months later. That lameness is usually permanent.


My dog is overweight. Does that relate to this injury?

A special note is appropriate concerning the dog’s weight. Obesity or excessive weight can be a strong contributing factor in cruciate rupture. The ligament may become weakened due to carrying too much weight; this causes it to tear easily. Obesity will make the recovery time much longer, and it will make the other knee very susceptible to cruciate rupture. If your dog is overweight it is worth consulting your veterinary surgeon regarding the problem. Various weight reduction programmes are available and will assist weight reduction.