Torn Anterior Cruciate Ligament
By Margot B. Schwag, VMD
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            The cruciate ligaments are two structures in the stifle (knee) which help to stabilize the joint. They keep the Femur and the Tibia from grinding back and forth on each other. If either or both of these ligaments are torn, the result is an unstable joint. Often the Menisci (cartilages) are also damaged with the injury, leading to even further instability. The resultant grinding back and forth of the structures in the joint leads to inflammation, eburnation (wearing away of bone), osteophytes (bone spurs), cartilage damage, and eventually painful arthritis.


            Surgery will help to minimize these changes. However, success depends on many factors, most of which are beyond our control. Some of these factors including the amount of cartilage damage, osteophyte formation, and whether one or both cruciate ligaments are torn, can be evaluated at the time of surgery. Other factors including an underlying immune mediated problem, strength of the scar tissue, and how long the sutures remain intact, we may not know for months. Two factors that we do have control over are weight and exercise. If your pet is overweight, we will need to start a weight loss program after the surgery has had time to completely heal. An exercise program to slowly strengthen the stifle is described later. Although surgery will minimize and delay the onset of arthritis, we are never going to have a completely normal leg, because there are no materials available to completely replace the original ligaments.


Cruciate Surgery

Your pet has just had surgery of the stifle (knee) to correct an instability caused by a torn cruciate ligament. Unfortunately, the ligament is usually torn to shreds and cannot be repaired, and at this time there is nothing available to replace the torn ligament.


The surgery has three main components.

  1. Opening the joint and removing the torn ligament, any damaged cartilage. fibrin or other debris.

  2. Tightening the joint capsule so that it acts like a splint to help stabilize the joint.

  3. Placing very strong sutures in such a way that they will do the job of the missing cruciate ligament.


What To Expect After Surgery

Immediately after surgery expect to have a fair amount of swelling and possibly some bruising. Occasionally there may be a clear to pink colored discharge, especially after they have started to move around. It is usually 7 to 10 days before they will put the leg down and 10 to 14 days before they use the leg for anything other than balance. Antibiotics will be dispensed to help avoid infection in the joint. We want your pet to be uncomfortable enough when walking that they don’t abuse the leg. However, we want them comfortable when they are at rest. A Fentanyl patch will be applied to prevent pain. If they appear to be in pain when lying down, other pain killers will be dispensed.


Basic Instructions

For the first two weeks exercise should be severely limited (i.e. going out to the bathroom) and should always be on a leash.

  1. Avoid stairs because they are difficult to maneuver on three legs and a tumble could be disastrous.

  2. The second two weeks will be spent going for walks (on a leash). Start with short ones and gradually increase their length. If they seem very sore after the walks, make them shorter. NO RUNNING OR JUMPING.

  3. The third two weeks will be spent going for even longer walks and possibly, if they are able, some short jogging.

  4. The fourth two weeks they can do a little running, but avoid sharp turns and jumping.


Progress Reports

Your pet should be rechecked when they come back to have the fentanyl patch off. Sutures are removed 10 to 14 days after the surgery. Unless there are problems, call to report how everything is going about every two weeks. If something doesn’t seem right, please call! A veterinarian would much rather say “That’s normal” than “I wish that you had told me that last week.”


Long Term Concerns

Please remember that the leg is never going to be a completely normal leg. There are no materials, natural or artificial, to completely do the job of the missing cruciate ligament. Abuse of the leg (i.e. jumping or sharp turns) is more likely to result in further injury to the stifle, so please avoid them. Expect your pet to exhibit some stiffness in the joint, especially after periods of rest, exercise, or inclement weather. Occasionally, the body can react to the suture material necessitating its removal. As with all joint injuries, arthritis can develop with time. However, most pets will have a long, comfortable life.


© 2000 Margot B. Schwag, VMD. All rights reserved. For permission to reprint contact author at Landisville Animal Hospital, 3035 Harrisburg Pike, Landisville, PA 17538