Canine Cranial Cruciate Ligament Disease

The dog’s stifle (which is equivalent to our knee) is stabilized by many ligaments. There are two bands of fibrous tissue called the cruciate ligaments in each knee joint. They join the femur and tibia (bones above and below the knee) together so that the knee works as a hinged joint.

They are called cruciate ligaments because they “cross over” inside the knee joint. One ligament connects from inside to outside the knee joint and the other outside to inside, crossing each other in the middle. They prevent abnormal forward and backward movement of the bones in the knee.

This is most often seen in dogs when running and suddenly changing direction so that the majority of the weight is taken on this single joint. This injury usually affects the cranial (front) ligament. The joint is then unstable and causes extreme pain, often resulting in lameness. It is now believed that most cruciate ligament disease in dogs is of a more chronic nature which results from weakening of the ligaments over time. The ligament may become stretched or partially torn and lameness may be only slight and intermittent. With continued use of the joint, the condition gradually gets worse until rupture occurs. The typical scenario is that the dog is chasing a ball, running around in a field or even jumping up on to something. The dog is suddenly lame and often none weight bearing on a hind leg. It may not be terribly painful to touch but very painful to walk on.

Diagnosis is usually made by manipulation of the knee, although many dogs need to be sedated to get proper relaxation and examination of the knee. During the examination, the veterinarian will try to demonstrate a particular movement, called a drawer sign. Other diagnostic tests such as radiographs (x-rays) may also be necessary.  

Dogs less than 20lb often do well without surgery. This may not apply to the 15lb agility dog as the level of activity desired may result in needing surgery. Geriatric dogs with other medical problems where anesthetic is a major concern may function ok without surgery but often times retired athletes are still very active and do much better after surgical repair.

Dogs weighing more than 20lbs (especially athletic dogs) need to have surgery to prevent rapid degeneration of the joint and arthritis. Each dog should be treated as an individual. A 50lb border collie that is active in high level agility may need a more stable repair than a 90lb golden retriever couch potato. Weight definitely plays a role and many of the dogs that I see with cruciate injuries are overweight.

Once the knee has been damaged, it will never be totally normal. With rapid surgical intervention and proper rehabilitation we can greatly slow down the onset of arthritis and regain almost totally normal function of the knee. This is not an emergency surgery but if possible it should be repaired with in several weeks of occurrence. The longer the time is between injury and repair, the more likely the development of arthritis. There are other concerns with waiting too long. Instability of the joint will increase the risk of damage to the cartilage (also called the meniscus). The prolonged lack of use of a leg will lead to muscle atrophy from lack of use of the leg. For every day of muscle loss (which starts from the day of injury) it takes 3 days to regain it. Studies have shown that dogs continue to lose muscle mass in their thigh for 5 weeks after cruciate ligament repair.  If you do the math you can see that this will have serious implications in the short term for a high performance dog. The most serious secondary problem is damage to the other knee due to the increased weight placed on it. It is estimated that up to 40% of dogs will rupture the cranial cruciate ligament in their second knee within 1-2 years of surgery on the first one.

There are many different surgical techniques but they all should involve exploring the joint and removing the pieces of the torn ligament. The cartilage should also be examined as it is often damaged as well. If damaged, the cartilage should be removed. There are many techniques to repair cranial cruciate ligament tears but they all centre on stabilizing the joint. Currently the most common technique is called an extracapsular repair which involves placement of high test nylon around the back and side of the knee (see picture). This results in immediate stabilization of the knee and allows early rehabilitation. Over time the suture will stretch and even break but by that time enough fibrous tissue develops around the joint to support itself. Possible complications (although rare) associated with this repair are suture breakage or stretching, infection progression of arthritis in the joint.

A model showing an Extracapsular Repair

The newest surgical technique to repair torn cranial cruciate ligaments in dogs is the tightrope procedure.  Tightrope CCL is an extracapsular technique which uses lateral suture stabilization in conjunction with a virtually indestructible material called FiberTape for knee joint stabilization. Fiber Tape is used to connect bone to bone and is held in place on the bone via metal anchors and small holes drilled through the bone.  The surgeon makes a few small incisions to access the points of attachment to the bone.  While the Fiber Tape will eventually degrade and possibly break over time, it is thought of as a superior material for larger dogs due to its greater durability and strength – buying your dog more recovery time.

An xray of a dog’s knee after a Tightrope Repair

There is a new repair technique that has been developed in the last 10years. This is called the tibial plateau leveling osteotomy (TPLO). It is based on the premise that cruciate injury is a result of too steep of an angle on the joint surface of the tibia (shin bone) ( see above line drawing) This causes an increased forward movement of the tibia with respect to the femur and stress on the cranial cruciate ligament. The surgery involves cutting the tibia and rotating the joint surface so that the tibial plateau angle is decreased resulting in decreased forward thrust of the tibia. A bone plate is applied to stabilize the tibia. The advantages of a TPLO are that the dog may have more rapid return to athletic potential as compared to the traditional techniques. Many canine athletes can return to athletic function 3 months after cruciate repair via TPLO although after 6-12 months there is really very little difference between TPLO and extracapsular repair. It has been proposed that a TPLO repair will slow down the progression of arthritis in the knee. On the other hand there are disadvantages to TPLO surgery. Complications can be more severe then traditional techniques.  It is more invasive as the leg is actually fractured and then repaired with a plate. Initially after surgery there is increased pressure on the front of the knee and the knee cap (patella). This can result in tendonitis and even breakage of the front of the tibia (tibial crest avulsion). There may also be loosening of the screws or improper healing of the fracture. These complications are rare and usually due to lack of exercise restriction in the first 4-6 weeks after surgery. TPLO surgery is also much more expensive than traditional repairs. I think that it is a good idea to consider a TPLO in canine athletes where a high level of athletic ability is desired. On the other hand I have seen canine athletes return to high athletic ability.

When contemplating any cruciate repair you must also consider the surgeon. I perform many extracapsular cruciate repairs but I do not perform TPLOs. The TPLO repair is highly technical and requires special equipment and expertise. I always recommend a board certified surgeon for a TPLO repair and they need to do a lot of them to get good at it. If you do not have a TPLO surgeon near you then this may be a factor in your decision making.

Whatever your decision with respect to surgical intervention, I believe that the post operative period is as important as the surgery. Studies have shown that post operative physical rehabilitation will reduce muscle atrophy and speed up weight bearing and return to function. From my own experience, I also believe that physical rehabilitation after cruciate ligament repair results in a reduced incidence of rupture of the opposite leg. 

One of the biggest factors with respect to recovery is weight. The first thing that I do with a dog that has ruptured a cruciate ligament is put it on a diet. Although not usually a problem in the canine athlete, obesity has an obvious negative effect on cruciate ligament recovery. But a normally active dog is going to gain weight if its activity is reduced but its food intake is maintained at the performance level. I would recommend that any athlete that has an injury should have its caloric intake decreased by 20-25% until it is back to work. A normally very active dog is going to gain weight when its activity is reduced for surgery and rehabilitation.

Beginning immediately after surgery we ice the leg as much as possible to reduce pain and swelling. Starting the next day we want to encourage weight bearing on the leg. The days of cage rest and bandaging are gone!!! We send the dog home on anti-inflammatory medication for 5-10 days to reduce pain and encourage early usage.

Icing after knee surgery as the dog is recovering.

We also start K-laser therapy immediately after surgery and continuing over the next 2-3 weeks. Laser therapy helps to reduce pain and swelling and promote healing. For more information see www.spot-check.com

K-laser therapy

Most of the rehabilitation is done at home by the owner. We train the owner to do range of motion exercises, stretching and massage (as well as icing) to reduce pain, swelling and atrophy due to lack of use. I also use weekly injections of a drug called cartrophen which increases joint fluid production which helps to reduce pain and heal the joint. I recommend that all dogs with any kind of joint problem (whether it be early arthritis or a cruciate rupture) take a glucosamine /msm supplement forever. Starting in the second week after surgery we use neuromuscular electrical stimulation 2- 3 times per week. This passes an electrical current through the muscles and causes a contraction. It simulates use of the muscles to reduce pain, prevent atrophy and hasten recovery.   We continue this for 1-3 weeks until the dog is using the leg enough to work the muscles on its own.

Electrical stimulation of the thigh muscles

Starting about a week after surgery we start dogs walking slowly on a land treadmill. The belt passing under the feet increases extension of the knee and also promotes weight bearing in the operated leg.

One of the best types of therapy for these injuries is hydrotherapy. Underwater treadmill walking can start as soon as 7-10 days after surgery but swimming should not start until at least 4 weeks after extracapsular repair or 6-8 weeks after TPLO.

Underwater treadmill walking after extracapsular repair

As each week passes we increase exercise to strengthen the joint and muscles and retrain balance and co-ordination. We use leash walks, hill walking and progress to pulling weave poles, figure eights, cavellettis and even tunnel work. Agility dogs do wonderfully with rehab as they already know a lot of the exercises! It is very important to note any stiffness or pain that occurs after exercise sessions. If this occurs then we have to step back on exercise and slow down the level of activity. It is very important that the dog be as pain free and comfortable during all stages of rehabilitation. Usually with in 1-2 weeks they are bearing more weight than before surgery and by 3-4 months post-op they are bearing full weight and can be back to full exercise. Cruciate ligament repair is an intensive and expensive surgery and so I always make sure that the owner is committed to the rehabilitation. Most owners of canine athletes want their dogs to return to a high level of function as soon as possible. Physical rehabilitation will improve the outcome and decrease the recovery time.

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