The cranial cruciate ligament (or CCL) is a ligament present in the knee that stabilizes the joint.  This ligament in people is called the ACL.  When this ligament is ruptured in dogs, it is usually from degenerative changes in the ligament that weaken it.  Large breed dogs such as Labrador Retrievers, Golden Retrievers, American Staffordshire Terriers and Pit Bulls, Rottweilers, Newfoundlands, and Akitas are predisposed.  Overweight dogs are also predisposed because of the extra weight and increase in inflammation in the joints because of their excess fat.  CCL tears are the most common knee injury in dogs.

There are two types of dogs we see with cruciate ligament trauma - one is a young, healthy, active dog who has suddenly become lame on a back leg.  Usually these dogs are running around in the back yard, the owner hears a yelp, and the dog is not using its back leg.  In most of these cases, the cranial cruciate ligament is likely damaged. 

The other dog that gets cruciate ligament trauma is the older, overweight, larger breed dog (or even smaller breed dogs that are overweight) that may have subtle smaller stretches or tears in the knee over time that go unnoticed or heal on their own.  With each subsequent trauma, the ligament gets weaker and weaker and eventually will tear completely.  This can happen when the dog jumps down off the bed or couch, is running in the yard, or just simply taking a misstep can sometimes be enough to break the already weakened ligament.  These dogs will also be severely lame.

There are some fairly accurate findings on physical exam that lead us to suspect a CCL tear.  These are:

• A failed "sit test" - When a normal dog sits, the knees should be under the body with the knees facing forward.  In a dog with knee pain, the injured knee will be held out and turned out away from the body.
• Swelling in the knee joint - A puffy knee means that there was trauma inside the joint.  A veterinarian can palpate the knee and tell if the swelling is inside or outside the knee joint.
• Cranial drawer sign - The veterinarian will place one hand on the end of the femur (thigh bone) and the other on the tibia (shin bone) and press the tibia forward.  In normal knees (because of the action of the cranial cruciate ligament) the tibia cannot move forward independent of the femur.  In dogs where there in a CCL rupture, the tibia can freely move forward in relation to the femur.  This is called a drawer sign and only occurs with CCL rupture.
• A clicking sound or grinding feeling inside the knee - There are structures called the meniscus which separate the two leg bones, allowing for a sort of shock absorption and cushion so bones do not rub together.  The cranial cruciate ligament attaches to one of the menisci.  In some cases, this meniscus can tear and we can hear or feel this as a clicking or grinding motion inside the knee.  

Usually physical exam findings are all that is necessary to actually diagnose a CCL rupture, but we usually will recommend x-rays.  This will help us to determine if there is already arthritis in the joint, to make sure there are no bone chips or other problems in the knee, and evaluate how badly the knee is affected.  In some dogs, especially heavily muscled ones, we may not get a cranial drawer sign because the dog is too stiff, and x-rays are a helpful tool to make sure we have made the correct diagnosis. 

There are both medical and surgical treatments to CCL ruptures.  Surgical treatment is by far the better option for any dog with a CCL rupture.  Any dog with an injured cruciate ligament will develop degenerative joint disease later on in life, but those treated surgically will have a much lower risk of developing severe arthritis.

Medical Management

• REST - this is the most important part of treatment for any injury, and usually the hardest to comply with, because a dog won't listen when you tell him to stay off his knee for 4 weeks!  But if surgery is not an option, complete rest for a minimum of 30 days is imperative.  This means no running, jumping, climbing stairs, or any other form of exercise.  All dogs MUST be leashed outside at all times, even just to use the bathroom.  We have had countless dogs feel better at the 2-3 week mark, be allowed to run outside to use the bathroom, and re-injure their knee and have no option but to go to surgery!  We advise crating your dog while you are gone or having the dog confined to a room where limited movement is available. 
  
• Anti-inflammatories (NSAIDs) - Rimadyl is usually the medication we use to treat inflammation in the knee when a CCL rupture occurs.  This is the dog equivalent to ibuprofen, but it is much safer than human NSAIDS.  NEVER use Advil, Aspirin, Tylenol, or any other human medication as these can cause serious side effects and possibly death. 
  
• Omega 3 Fatty Acid Supplements - recent studies have proven the benefit of using a fatty acid supplement to help decrease inflammation in arthritis, trauma, and many other conditions.  It actually decreases the chances of the other CCL rupturing in the future as well.
• Weight loss - overweight dogs are highly likely to have a rupture in their other CCL within 1-2 years after their first injury.  Keeping a lean body condition is vital to decreasing problems in the future with this as well as early onset arthritis in the injured knee.
• Dasuquin - this is a joint supplement containing glucosamine and chondroitin sulfate, two substances responsible for good cartilage and joint health.  This supplement can help improve pain in dogs with mild to moderate arthritis or joint disease.  A side note:  this is a veterinary FDA approved product, and so it has to be batch tested to make sure there is active ingredient in the bottles we are selling you.  OTC human glucosamine/chondroitin supplements are not regulated by the FDA, and so there is not a guarantee that you are getting the active ingredient you are paying for. 
  
• Prescription joint diets - these are great alternatives for people who can't remember or don't want to give supplements.  These diets have increased levels of fatty acids, glucosamine and chondroitin so your dog is getting all of these ingredients at every meal.  In some more severe cases, we may have to feed this diet and give additional supplements to achieve good results.
• Exercises/physical therapy - this is a long-term treatment once the initial injury has healed.  Exercises such as swimming, slow walking, cavaletti poles, and balancing exercises are very good to improve muscle function without placing too much stress on the joints.  Routine exercise will also help keep your dog at a good body weight.

Surgery
It is recommended that all dogs get surgery to stabilize their knees, check for meniscal damage, and prevent long-term severe arthritis.   There are several options for surgery, and at the time no one knows exactly which produces the best outcome.  We usually make recommendations based on individual dogs and personal experiences as well as specialists' recommendations.

1. TPLO - this is a surgery done by an orthopedic surgeon and is typically done more with large and giant breed dogs.  We can tell by doing a knee x-ray if the angle of the bones surrounding the knee joint will make a TPLO the better surgical option.  During this surgery, the surgeon cuts the top of the tibia and angles it in such a way that the dog's natural weight bearing stabilizes the knee joint.  The top of the tibia is then reattached with a bone plate.  The surgeon will remove damaged meniscus or cruciate ligament during the surgery, and can also cut away any bony spurs that have developed in the joint.  We tend to refer dogs with large amounts of arthritis to the specialists whenever possible because the surgeons do an outstanding job of addressing the bone spurs as well as meniscal tears.  This surgery also requires about 8 weeks of strict rest following the procedure with the dogs usually beginning to bear weight on their legs about 7-10 days after surgery.
2. Intracapsular repair - this surgery can be done in the hospital and provides good results for most dogs. We will perform a knee x-ray to evaluate the joint space and make sure this type of surgery will be appropriate. During the surgery, we enter the knee joint and remove any damaged meniscus and cruciate ligament flaps.  We then drill a small screw into the femur (thigh bone) and another hole through the tibia (the shin bone).  We then pass either a strong surgical filament or wire attached to the screw in the femur through the hole in the tibia and secure it tightly in a figure 8 pattern.  By doing this, we create a false ligament with the surgical filament.  This allows the knee to move in a normal motion. 
   

The outcome for your dog depends on a) what factors caused the CCL rupture, b) was medical therapy or surgery done to fix the knee and c) what post-operative steps are taken to prevent the other knee and other joints from having problems.  All dogs that rupture their CCL will have early onset arthritis - how much depends on what happened inside of the knee.  Dogs with long-standing arthritis or meniscal tears may have continued lameness regardless of treatment.  Overweight dogs that do not lose weight are likely to continue to have problems with their joints. 

Though in young, healthy dogs there is no way to truly prevent CCL ruptures from happening, there are steps that can be taken to minimize the risk.  These include:

• Keep your dog at a lean body weight (if you are unsure what that is, schedule an exam and we can discuss this with you!)
• Avoid extreme exercise in predisposed breeds - don't take your Labrador running 6 miles daily with you when he is 5 months old.  This will increase the stress on his joints before he is done growing and will lead to problems down the road.  Exercise is necessary for good overall health; just don't overdo it.
  
• Give a joint diet to predisposed breeds - certain breeds should be on a maintenance joint diet to help keep their body in good condition.  Though prescription joint diets work best, there are one or two OTC diets that may be beneficial. 
  
• Give a fatty acid supplement - recent studies have proven the benefits of these supplements in many different circumstances.  They can be used not only as a treatment but as a preventative supplement as well.  Be careful - not all supplements are created equal!  Just like the Dasuquin, there are some products out there that give much better results than others, and prescription products tend to work better.