Cruciate Ligament Repair

I know that knee injuries are common in people. Do they occur in dogs? The knee joint of the dog is one of the weakest in the body. Just as football players and skiers frequently suffer knee injuries, the dog also has knee injuries. 

Why is the knee so likely to be injured?

The knee joint is relatively unstable because there is no interlocking of 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.  When it is torn, 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 collapsing.

How is it diagnosed?

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 awake.  If the dog is in pain, has very strong leg muscles, or is uncooperative, it may be necessary to use sedation in order to examine the joint thoroughly.

How is it treated?

Correction of this problem requires surgery.  A skilled surgeon can fashion a replacement ligament and stabilize the joint so it functions normally or near normally.  If surgery is not performed within a few days to a week, arthritic changes will begin that cannot be reversed, even with surgery.

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 removed if necessary.

How is it treated?

Correction of this problem requires surgery.  A skilled surgeon can fashion a replacement ligament and stabilize the joint so it functions normally or near normally.  If surgery is not performed within a few days to a week, arthritic changes will begin that cannot be reversed, even with surgery.  Generally there are two different surgeries that can be performed to correct this problem

Tibial Plateau Leveling Osteotomy (TPLO)

This procedure involves changing the anatomical slope of the tibial plateau (the top of the shin bone). Doing this reduces or eliminates the instability caused by the loss of the cruciate ligament.  The surgery requires cutting the tibial bone and then placing 1-2 bone plates to stabilize the cut bones.  Recovery is quicker than with the external capsular technique, and generally dogs are weight bearing on that leg about 2 months post surgery.  It is very important that you make plans to restrain your dog and ensure strict rest for 2-3months to allow the bone to heal properly. 

Tibial Tuberosity Advancement

This procedure has the advantages of early return to function like the Tibial Plateau Leveling procedure but has fewer expensive implants.  It has had excellent results over the past 3 years.  

External Capsular Stabilization

This procedure involves stabilizing the stifle(knee) by tightening the joint capsule that surrounds the knee.  A nylon band is then placed alongside the joint capsule to further reduce instability.  This technique has been practiced for over 30 years and shows similar success to the TPLO procedure.  However it takes longer to return to full weight bearing, approximately 3-4 months.  Also, while we have performed the external capsular stabilization on dogs as large as 130 pounds, it seems to work best for dogs less than 100 pounds.

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 cannot be corrected.

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

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 has a weight problem, there are prescription diets that can be used to assist weight reduction.