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

Just as football players frequently suffer knee injuries, dogs are 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.

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.

How is it treated?

Correction of this problem requires surgery. A skilled surgeon can fashion a replacement ligament or change the angles and forces within the joint to stabilise it so that it functions normally or near normally. Arthritic changes will begin that cannot be reversed, even with surgery. However surgery stabilises the joint and this slows down the arthritic change. There are many available techniques but two most commonly used are De Angelis procedure and TTA (Tibial Tuberosity Advancement).

De Angelis can be used successfully on dogs under 25 kg and cats. It involves drilling two holes in the tibia and passing suture material through the holes and around a small bone behind the femur. When this artificial ligament is placed it stabilises joint significantly and arthritis is less likely to happen. The leftovers of the cruciate ligaments and damaged meniscus (if any) are removed and the joint is flushed thoroughly. The joint capsule is tightened and the wound sutured in multiple layers.

Recovery period is 3-6 months and exercise is slowly introduced. With time the artificial ligament will get lose and thickened joint capsule will take over the role of the cruciate ligaments.

TTA is one of the latest methods in which a small wedge of tibia is removed and a special implant is put in place. The objective of the TTA is to advance the tibial tuberosity, which changes the angle of the patellar ligament to neutralise the tibiofemoral shear force during weight bearing. By neutralizing the shear forces in the stifle caused by a ruptured or weakened cruciate, the joint becomes more stable without compromising joint congruency. The knee joint is not stabilised as such but due to changes in the biomechanics of the knee joint the lameness resolves quickly. This procedure is used on all dogs over 25 kg because they put too much pressure on artificial ligaments if De Angelis procedure would be used. Like in De Angelis procedure the joint is examined and damaged parts removed.

Post operative care
All patients that underwent the surgery must rest and exercise has to be gradually introduced. Physiotherapy can be very beneficial and even is rather basic, such as flexing and extending the knee joint 15-20 times 2-3 times a day, makes all the difference. Carthophen injections (Pentosan) work very well on damaged joints and reduce recovery time in 80% of cases.

If you have any questions, please contact your local Vets4Pets practice.