Cruciate Ligament Injuries In Dogs

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Cruciate ligament injuries not only cause a great deal of pain and discomfort for the dogs unlucky enough to suffer from them, they can also be very stressful for dog parents. These injuries are one of the most common causes of hind-end lameness, pain, and arthritis in dogs.

Since other conditions can also cause hind limb lameness (such as hip dysplasia, traumatic injuries like cuts, sprains, or muscle strains, displaced kneecaps, or ruptured discs in the spine), whenever a cruciate ligament injury is suspected it’s important to identify exactly what’s causing the issue. We humans tend to take the “watch and wait” approach when it comes to strains and sprains, but any dog who is limping severely should be examined by a veterinarian as soon as possible. Unlike humans, dogs don’t understand the concept of “taking it easy”, so the best approach is to have any dog who is limping severely examined by a veterinarian to prevent further damage.

The Cruciate Ligament – The Unsung Hero Of The Knee

So what exactly does the cruciate ligament do?

Ligaments are thick bands of connective tissue that connect two bones (or cartilage) at a joint. There are two cruciate ligaments located in each of the rear legs of dogs at the knee, or stifle. These ligaments connect the thighbone (femur) to the shin bone (tibia).

The word cruciate means “to form a cross.” In dogs, the two cruciate ligaments are called the cranial cruciate ligament (CCL) and the caudal cruciate ligament. These ligaments criss-cross over each other and work together to allow the knee to operate as a hinged joint. Since the knee itself is a relatively unstable joint, it’s the cruciate ligaments that are responsible for stopping the knee from twisting or overextending.

In dogs, the cranial cruciate ligament (CCL) is the main supporting ligament that helps stabilize the knee. (It’s identical to the anterior cruciate ligament, or ACL, in humans – the one that football players always seem to injure). Like its human counterpart, the CCL is the most commonly torn (or ruptured) ligament in the knee. When the CCL tears, it can be a partial tear, or a complete rupture.

How Do Cruciate Injuries In Dogs Happen?

Although we tend to think of cruciate ligament injuries as resulting from sudden trauma (such as a twisting injury to the knee), in dogs this is actually rare. Most cruciate tears in dogs occur because the cruciate ligament has been gradually deteriorating over a period of many months to years.

As dogs age, their cruciate ligaments can slowly begin to degenerate, causing the knee joint to become unstable. This makes them more prone to injury. Although it’s certainly possible for sudden injuries to occur to healthy cruciate ligaments in dogs, it’s far more likely to happen due to smaller, repetitive injuries over time.

Dogs who seem to be more prone to suffering cruciate ligament injuries include:

• Large and giant breeds, especially those with relatively long legs
• Dogs who are overweight, since extra weight places a higher level of stress on joints
• Dogs with other knee problems, such as luxating patella
• Very active dogs who regularly engage in strenuous activities that include lots of  jumping (such as for balls or frisbees)
• Dogs who have already previously injured a cruciate ligament in one knee (they are at higher risk for injuring the other knee as well)
• Dogs who are spayed or neutered at a very young age. Evidence suggests that sex hormones appear to have a protective effect on the musculoskeletal system, making dogs who are neutered at less than 6 months of age more prone to cruciate ligament injury. However, this is still being studied.

Certain breeds of dogs also appear to be predisposed to cruciate injuries, including Akitas, Labrador Retrievers, St. Bernards, Mastiffs, Newfoundlands, Rottweilers, Staffordshire Terriers, and Chesapeake Bay Retrievers.

Signs Of Cruciate Ligament Injury

Signs of cruciate ligament injuries in dogs include:

• Sudden, severe limping on a rear leg, often preceded by the dog crying out at the exact moment of injury.
• Noticeable swelling in one knee.
• An inability to bear weight on the injured knee. Many dogs will “toe touch”, placing just the toes down on the injured leg instead of the entire foot.
• The dog not being able to sit squarely, instead kicking one leg out to the side when he sits down in an attempt to shift weight away from the damaged knee.
• Difficulty getting up or jumping up into a car.
• A noticeable popping noise when walking.
• A decrease in the muscle mass and a progressive weakening of one leg (if the injury is left untreated over time).

Diagnosing A Cruciate Ligament Injury

If you suspect your dog has a cruciate ligament injury, it’s important to seek veterinary help as soon as possible. If a cruciate ligament tears and no treatment is provided, the dog will limp for several weeks, then appear to get better; however, the knee joint will remain permanently unstable. Then over time, every time the dog puts weight on the knee, the tibia (shin bone) will slide forward across the femur (thigh bone). Not only is this extremely painful, it also causes the cartilage in the knee to wear down, leading to arthritis.

Your veterinarian can diagnose a cruciate ligament injury by performing a simple physical examination of the knee while your dog is under sedation. If the cruciate ligament is completely torn, when your vet manually moves the knee he or she will see a distinctive movement called an “anterior drawer” sign (where the knee moves side-to-side like a drawer in a cabinet, instead of feeling like it’s locked in place.)

If the cruciate is only partially torn, x-rays or an MRI can be done to diagnose the injury. In some cases, the vet may recommend arthroscopy, where a small telescope with a camera inside is inserted through a small incision in the knee to give a definitive view of the ligament. This procedure requires general anesthesia.

Treating Cruciate Ligament Injuries In Dogs

If your dog has a cruciate ligament injury, the best treatment option will be depend on many factors, including your dog’s age, size, activity level, weight, physical condition, and whether the ligament is partially or completely torn.

Partial cruciate tears can sometimes improve after a period of rest and restricted activity, often combined with anti-inflammatory medications. However, this approach generally works better for smaller dogs (under 30 pounds) who are not overweight and not extremely active. Unfortunately, many partial tears will eventually progress to full tears, which almost always require surgery.

Surgical treatment is usually recommended as the best way to permanently correct a cruciate ligament tear and restore stability to the knee joint. During surgery, the veterinarian removes fragments of the torn ligament, repairs the surrounding cartilage if needed, and creates an artificial ligament to stabilize the joint. There are several different surgical procedures for fixing cruciate ligament tears in dogs. Currently one of the most preferred surgical methods is called a “tibial plateau leveling osteotomy” (TPLO), which seems to work especially well for larger, more athletic dogs.

Care After Surgery

If your dog needs cruciate surgery, it’s important to understand the type of care he will need afterwards. For best results, this usually involves the following:

• Severely restricted activity for at least 2 weeks after surgery, followed by careful supervision and reduced activity for another 4 to 6 weeks.
• The use of pain medication and NSAID’s (non-steroidal anti-inflammatories) to control pain and swelling.
• A reduced calorie diet for dogs who are overweight.
• The use of joint supplements such as glucosamine and chondroitin to aid in the formation of new, healthy cartilage.
• Physical therapy, such as the use of underwater treadmills to reduce pressure on damaged and healing joints and increase muscle strength. The use of physical therapy has been proven to greatly increase recovery and healing time.
• The use of alternative therapies to speed healing, which can include acupuncture, massage, and laser therapy.

Prognosis For Dogs With Cruciate Ligament Injuries

The long-term prognosis for dogs who have undergone surgical repair of a damaged cruciate ligament is quite good, with a success rate of approximately 85-90%. The type of surgical technique used, the skill and experience of the surgeon, and the type of rehabilitation therapy and long-term joint management has a lot to do with how successful the outcome will be.

Unfortunately, for dogs who have suffered a cruciate ligament injury in one knee, estimates are that 40-60% of these dogs will go on to develop the same injury in their other knee. Since being overweight can greatly increase a dog’s risk of cruciate ligament injury, weight management is very important in preventing injury to the healthy knee, as well as re-injury to the knee that was operated on.

It’s important to realize that regardless of whether your dog’s knee is surgically corrected or managed with rest and medication, arthritis is still likely to develop in the injured knee as your dog ages (although this is thought to happen more slowly and to a lesser degree if the knee is surgically corrected). Because of this, any dog with a cruciate ligament injury will need to have medical management for the remainder of his life to help slow the development of arthritis.

If you suspect your dog has suffered a cruciate ligament injury, please don’t delay and seek veterinary attention as soon as possible. By promptly treating the injury, you can avoid further pain, debilitation, and the onset of problems caused by arthritis down the road.

Have you ever had a dog with a cruciate ligament injury? If so, how did you treat it? Please share your story with us in the comments below!