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.
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.
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.
Correction of this problem requires surgery. A skilled surgeon can fashion a replacement ligament and stabilise the joint so it functions normally or near normally. Massive arthritic changes will begin that cannot be reversed, even with surgery.
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.
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.
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.