Features March 2019 Issue

Torn Cruciate Ligaments in Dogs

Cranial cruciate ligament tears are very common in dogs. Learn how these injuries happen, and what you can do to try to prevent them.

Many dogs are amazing athletes, capable of running faster, jumping higher, and displaying better endurance than most human sports stars. But even when they are not very athletic, dogs are hard on their joints, particularly their stifle joints. The dog’s stifle is analogous to a human knee and is commonly (and interchangeably) called a knee or a stifle.

One of the most common athletic injuries in humans is damage to the anterior cruciate ligament (ACL) in the knee. If they haven’t torn it themselves, most people know someone who has. In human athletes, this is known as the “plant and twist” injury. It’s seen most frequently when the foot is planted firmly and the knee is then either twisted or run into (picture those cringe-worthy clips of soccer and football players being hit from the side).

In dogs, we see this same injury, often resulting from the same sort of forces, but we also see chronic wear and tear leading to cruciate ligament tears. To fully understand why this is so, you need to appreciate the mechanics that lead to cruciate ligament injuries.

canine stifle lateral view

The cranial cruciate ligament prevents the tibia from moving forward in relation to the femur. When it tears, joint instability and pain (resulting in lameness) result. A veterinarian who suspects a tear of the CrCL will try to manipulate the joint and see if she can get the tibia to move forward; this is referred to as the “drawer test” (because if the CrCL is torn, the tibia will slide forward like the opening of a drawer.)

Canine Knee Anatomy

The knee joint in a dog is the point where the thigh bone (femur) and “calf bones” (tibia and fibula) come together and interact. Refer to Figure 1 (right) so you can fully understand what the dog’s knee is up against, literally and figuratively! Here are the anatomical terms you’ll need to know:

Femur – Upper leg bone extending from the hip to the knee.

Tibia – Primary lower leg bone extending from knee to ankle.

Fibula – Secondary lower leg bone extending from knee to ankle.

Stifle – Knee joint.

Cranial cruciate ligament (CrCL) – This ligament provides front-to-back stability (and a tiny bit of rotational stability) between the femur and tibia in the knee joint.

Meniscus – C-shaped cartilage cushion that provides shock absorption in a joint.

Dog Knees vs. Human Knees

Picture your dog standing: His knee joints are slightly bent, ready to propel him forward like a coiled spring. Now picture yourself standing next to your dog: Your knees are straight, possibly even locked in place. The disparity in the posture of our knees when we are standing is one of the biggest differences between dogs and humans – and it contributes to the frequency of injuries to dogs’ knees.

The bottom of the femur is rounded in both dogs and humans. The top of the tibia is flat. When a human is standing, that round femur rests neutrally on a flat surface. It takes very little effort to keep that position – and gravity helps. A round structure on a flat surface will pretty much stay in place, as long as that flat surface is level.

Now, think back to the dog. His knee is bent. That means that the round end of the femur is on a tilted platform. Something needs to keep that femur in place.

That something is, in large part, the cranial cruciate ligament. As the name implies, the cruciate ligaments – both caudal (toward the tail) and cranial (toward the head) – form an “X” in the knee joint, holding the femur to the tibia. The cranial cruciate ligament starts at the back of the femur and attaches to the front of the tibia. It is constantly being strained by the natural position that the dog stands in. The slope to the top of the tibia, combined with the round end of the femur, means that the femur is always trying to fall off the back of the tibia.

dog knees flexed while standing

Dogs’ knees are usually flexed; their cruciate ligaments are under tension when the dog is standing, holding the femur in place on the angled tibia. In contrast, our cruciate ligaments are in their least-stretched position when we are standing, as our femurs rest relatively securely on our tibias when we stand.

Ligament Tears in Dogs More Common Than in People

A loose string can be moved around with little risk of breakage, but the more you increase the tension on the string, the easier it will tear. The same is true of a ligament. So, in dogs, with this ligament under constant strain, tears are more common than in the human knee. In fact, this is the most common orthopedic injury that veterinarians see. In humans, this ligament gets periodic “rest” breaks and is really under strain only during physical activity. In dogs, it is in constant use – and over time, especially in large-breed or overweight dogs, it wears out.

A CrCL injury in a young, healthy dog is typically an athletic injury. In older dogs, it is usually an injury of chronic wear and tear. This explains why it’s so common for a dog who has damaged the CrCL on one side to then tear it on the other side. When you take one back leg out of commission, the work load shifts to the other, increasing the strain on the ligaments of the “good” leg.

This is simplifying things a bit. There are many contributing factors to this type of injury, from the dog’s build (conformation) to his activity level. Some things that can predispose a dog to this type of injury include obesity, a sedentary lifestyle, and other joint problems (such as “trick” knee caps). Overweight dogs experience far more strain on their joints than their fit counterparts. Dogs who are not very active also strain their ligaments more, as their untoned muscles don’t contribute much to the task of holding things in place.

Dogs Don't Have ACLs (They Have CrCLs)

The ligament that provides front-to-back stability in the knee is called the cranial cruciate ligament (CrCL) in the dog, but the same ligament in the human knee is called the anterior cruciate ligament (ACL). Why the different anatomical names?

It has to do with how the front of a quadriped (four-legged animal) is described as compared to the front of a biped (two-legged animal).

In a quadriped, the “cranial” refers to the head end of the animal. The cranial side of the dog’s knee is the side closest to his head.

In an upright biped like a human, the same surface of the knee (as just one example) can’t accurately be described as being closest to his head. Instead, the “front” is called the anterior or ventral surface.

This can be confusing, especially when people refer to a dog’s ACL. It’s not the correct term, but when it’s used, it is meant to indicate the CrCL.

To add to the confusion, the cranial cruciate ligament is sometimes abbreviated as CCL and sometimes as CrCL. Since CCL could also stand for caudal cruciate ligament, we prefer the more precise abbreviation of CrCL.

Dogs Most At Risk for Torn Cruciates

Let’s look a bit deeper at the patients who most commonly present with this injury: small dogs, young big dogs, and old big dogs.

When a small-breed dog, young or old, is diagnosed with a torn cruciate ligament, it’s very important to check for a specific, concurrent problem – medially luxating patellas. This is a fancy way of saying knee caps that slip to the inside of the joint. This is a very common congenital problem for dogs under 20 lbs. When they are born with knee caps that move incorrectly, they are at higher risk for ligament tears because of the abnormal forces on the joint. This is important because it can and should be fixed at the same time as a torn cruciate ligament.

When a young large-breed dog is diagnosed with a torn cruciate, I look for conformation problems. Do his legs bow like a cowboy? Do his paws turn out like a duck? I also ask about activity level, since these are the dogs who will most commonly get this injury through athletic injury, just as with humans.

If it’s an older, bigger dog, it’s usually a wear-and-tear injury, which increases the risk for a tear in the other back leg.

All of these dogs have one thing in common, though: Their risk of a ligament tear is lower if they are fit and at an appropriate weight! Overweight dogs are at a much higher risk for joint problems in general, from arthritis and strains to fractures, dislocations, and ligament tears. Keeping your dog (young or old), active and at a healthy weight will stave off many potential problems.

small dog leaping

Many tiny and small dogs have medially luxating patellas – kneecaps that can move out of position. If they tear a CrCL, the luxated patella should be surgically corrected at the same time the knee ligament is repaired.

Diagnosis of Canine Cruciate Ligament Injuries

So now we know the anatomy and the “why” of this injury. Let’s talk about how it’s diagnosed. Any dog who comes in with a back leg limp should be checked for a torn cranial cruciate ligament.

The first clue is a knee joint that feels swollen. Anytime the knee joint is swollen I am on high alert for a ligament tear.

To look for this injury, veterinarians do something called a “drawer test,” which involves moving the tibia in relation to the femur. If I can move the lower leg bone forward in the knee, the cranial cruciate ligament is not doing its job. Sometimes, in a big, strong dog, this requires sedation. But in small dogs, it’s pretty easy to do during a routine physical exam.

Once this injury is suspected, x-rays are the next test. Now, let me say this and say it loud: YOU CANNOT SEE A LIGAMENT ON AN X-RAY. Nevertheless, x-rays are still very important, because they let us double-check for other injuries (such as small bone fragments) and help us evaluate whether arthritis might already exist.

The position of the leg bones (as seen in the x-rays) will also give us clues as to whether and how severely torn the cruciate ligament might be; certain changes in the position of the bones can indicate that the ligaments are not stabilizing the joint properly. Finally, x-rays also help with planning for how to treat the injury (which we’ll talk about in the next issue).

Complicating Factor

A torn meniscus is one concurrent injury that can be suspected, but not diagnosed, until surgery. This is another injury that’s common to both human and canine knees.

The meniscus is a little piece of cartilage that provides cushioning and shock absorption in the knee. When the cruciate ligament is torn, that cartilage starts getting squished and rubbed in an abnormal way, which can lead to tears in the meniscus. A chronically torn meniscus may lead to further arthritis and discomfort in the future. There is no good data on whether or not removing a torn meniscus improves long-term pain control in the joint. Some surgeons recommend removal and some do not, but that’s a discussion to have on a dog-by-dog basis with your doctor.

Future Options

The stifle is a complex joint with a lot of working parts. The joint is prone to injury because of the way it’s formed and the way it’s used in the dog. A cranial cruciate ligament tear is not an emergency, but it’s worth a trip to your veterinarian to talk about options.

Cranial cruciate disease is a constellation of signs and symptoms that have a lot of different management options. We’ll dig into those options in the next issue. Until then, keep an eye on your dog. I bet you’ll notice a lot more of the dynamics of his knees than you did before!

A 2011 graduate of Michigan State University’s College of Veterinary Medicine, Kyle Grusling, DVM, practiced emergency medicine for three years before switching to a general practice. Dr. Grusling works at Northland Animal Hospital in Rockford, Michigan.

Comments (15)

Our Coton de Tulear Jack was 10 years old when he tore his ACL. He could not put any weight on his rear right leg and consequently, could hardly walk and was in terrible pain. I took him to our Vet who said he needed surgery and would most likely need surgery on his other knee within a year. I thought there had to be a better way. This is when I was lucky enough to find Dr. Babette Gladstein. She came
to see Jack immediately and told me she could cure him without surgery. It would take several months of treatments with Laser, Ultrasound and Prolo Therapy. He would also have to wear a brace, on his leg, during the treatment time.
To make a long story short – Jack is totally cured! He’s about to turn 16 and is still in great shape. We are eternally grateful to Dr. Gladstein.

Posted by: nvines | March 21, 2019 2:17 PM    Report this comment

Dr. Gladstein did prolotherapy on my Akita and he's totally fine now

Posted by: dog lover333 | March 19, 2019 2:37 PM    Report this comment

Reading about acl ccl tears and dogs and several holistic or homeopathic or naturopathic veterinarians mention that overvaccination causes auto immune disease that can cause the immune system to cause inflammation in the CCL and damage the knee joints. Vaccination was cited as the main cause of weak acl or ccl joints and since overvaccination is so prevalent now in the usa, that is why so many dogs tear their knees. Before all these vaccines, a torn acl ccl was very rare.

Posted by: dog9 | March 13, 2019 9:57 PM    Report this comment

I have read most of the comments above and would love to share what I found for my 60lb little girl that was diagnosed with luxating patella's. She got the x-rays and ultrasounds etc. Surgery was risky due to her Addison's; and like the above orthopractic doctors, the surgery was not a 100%. Fast forward to 3yrs, and I found cold laser. I researched and found a fair price for a middle ground output of laser hand held device. (that place on the internet that has everything and begins with A...) I've used it now for three weeks, at least 20minutes daily, and she can now stretch forward after her 'playbow' stretch in the am! It elicits endorphins too and she lays there enjoying it. (she will be 5 this August 2019) I even use it on myself, I have bad knees too!

Posted by: TrainYourDog2 | March 10, 2019 10:57 AM    Report this comment

Reading about acl ccl tears and dogs and several holistic or homeopathic or naturopathic veterinarians mention that overvaccination causes auto immune disease that can cause the immune system to cause inflammation in the CCL and damage the knee joints. Vaccination was cited as the main cause of weak acl or ccl joints and since overvaccination is so prevalent now in the usa, that is why so many dogs tear their knees. Before all these vaccines, a torn acl ccl was very rare.

Posted by: dog9 | March 7, 2019 12:32 PM    Report this comment

This happened to my extra large lab retriever mix. After running hard, he was limping, then only able to walk on 3 legs. Then days later, a loud cracking sound, which I learned was the damaged meniscus. I went to vets & vet surgeons, all were adamant about selling tplo surgery but after researching the dangers of tplo, and pain and suffering and No guarantee the surgery would go well. After surgery, a dog may never walk normally again, I decided on NO surgery. With more research, came across the posh dog knee brace featured at the World Veterinary Expo. We tried the Posh Brace and it worked at supporting the knee for short dog walks right away. No cage time needed. We followed the posh protocol and in less than a month the cracking sound stopped, so the meniscus had healed. Then wearing the brace twice daily for dog walks and the dog walks were longer and longer, and his walking improved to normal. We kept using the posh brace for dog walks for many months to make sure the knee was better. He was walking normally in only a few months. He hasn't worn the brace for over a year now and has been walking fine ever since. With support of the posh brace, the other knee never failed. We never bought the painful tplo or tta surgery. I found the posh brace at poshdogkneebrace.com Best decision was avoiding the tplo or tta surgery nightmare. The posh brace made this possible. I had an interest free Care health credit card to buy the posh brace and then I was reimbursed 90% for the posh brace by my pet insurance.

Posted by: dog9 | March 7, 2019 12:21 PM    Report this comment

My Penny, a Samoyed/Sharpei/Collie mix, loves to run and chase squirrels and rabbits. Several years ago she suffered a Cruciate Ligament Rupture in her right hind leg and could put no weight on that leg. The vet told me the surgery would be $1,000. I couldn't afford it, so I researched homeopathic remedies and discovered Rhus Tox, which helps with injuries such as that. I was skeptical, but I used the 30C dosage multiple times per day as suggested and also used Ruta Graveolens. I crated her to keep her quiet, and prevented her from jumping up and down off furniture. I took her out to potty only on a leash and she wasn't allowed to run. The injury started healing when she injured the other hind leg. This time the vet said the surgery would be $1800. I couldn't afford that, so I did the same treatment. Today Penny is 13 years old and still running around. Though maybe not quite as fast, she is by no means handicapped. Now, whenever has any kind of sudden lameness I right away treat with homeopathic Arnica and 2-3 hours later follow up with Rhus Tox. If that doesn't resolve the issue, I use Ruta Grav. One is for use when the injury is better with movement, and the other for when it's worse with movement. The remedies are very inexpensive. A couple of months ago Penny was favoring her right front leg, so I started giving her a product at least once a day called Bosmeric, which contains boswellia, turmeric, ginger and black pepper. This has made a HUGE differnce. Within a couple of days she stopped limping. I also found another homeopathic treatment called Jump for Joynts, which has been amazing as well. I'm giving both of these as a preventative since the Cosequin I had been giving for years didn't seem to do any good.

Posted by: DLittle | March 6, 2019 9:58 AM    Report this comment

I went through two back-to-back CCLs in my dog Sunshine, a 22-pound white Malshi terrier. The second injury happened within weeks of the first, as I watched her jump off my bed. I immediately instituted a "no jumping" rule, which was disappointing as it meant a lot less cuddling.
I had delayed surgery for the first injury partly because I was doing research, concerned that TPLO would be too invasive for a small dog. I ended up finding a surgeon who repaired both CCLs plus a luxating kneecap for much less that the price I was originally quoted for a single TPLO. For what it's worth, the surgeon said that all the techniques have similar outcomes.
Within months after these events, Sunshine developed full-blown atypical Cushing's disease. The specialist we saw said that CCL injuries are common in Cushing's patients "Cushing's ... also causes lax ligaments and weight gain" (quoted from the 2ndchance website). Sunshine's repaired legs lasted for the rest of her short life.
I've also read that neutering, especially early neutering, may be associated with CCL because the ligaments become weaker:
"Across several breeds, a study of CCL found that neutered males and females were 2 to 3 times more likely than intact dogs to have this disorder" (cited from the NLM database). Sunshine was spayed at 16 weeks.
I've also heard that neutering may contribute to atypical Cushing's (see the Mercola website).
While none of these findings are confirmed and each dog is an individual, my two takeaways from Sunshine's CCL experience were: (1) jumping down off furniture is a serious risk factor for small dogs; and (2) I would delay neutering my next dog until the sex organs have matured.

Posted by: muriel33 | March 5, 2019 6:45 PM    Report this comment

My Airedale Cassie was my Mighty Hunter. She chased squirrels, bunnies, birds, cats, and she even brought me a dead opossum. She was a rescue, and at her first vet visit with me, the vet said she'd had a previous cruciate injury that had not been repaired. She blew out her other knee several years later. Our vet practice has an orthopedic surgeon, so the repair and her recovery went very well. It WAS pricey.

Posted by: ecutler | March 5, 2019 5:53 PM    Report this comment

Really great explanation of the anatomy and physiology of the dogs "knee" joint. I must agree with Asdf's comment from today about the doctor not addressing the issue of juvenile spay/neuters. Back in the day, I had all my dogs surgically altered at a young age (along with getting vaccines yearly and feeding what I now know are crappy foods before learning more from places like WDJ). One of my dogs blew both of her CrC's a couple years apart from each other. She was an active, athletic dog of an appropriate weight. She participated in agility, but blew neither knee while doing agility. She had TPLO's done on both "knees" and went on to earn multiple agility titles. Arthritis never was an issue in later life (with joint supplements), and remained active throughout her life, after retiring from agility at age 12.

Posted by: ResQdodmom | March 5, 2019 5:05 PM    Report this comment

This article is not complete without stating that neutering and spaying before the age of one or the first heat cycle predisposes dogs to torn cruciate ligaments later in life, as a result of their sex hormones not forming their cruciate ligaments properly. There are veterinary studies stating as such. Disappointed and surprised that wasn’t mentioned.

Posted by: Asdf | March 5, 2019 2:35 PM    Report this comment

Great article. My spaniel/herding dog cross blew both her CLs over several years and now at 14 years old is struggling with the inevitable arthritis. She was an agility dog, but wrecked her knees chasing foxes.

Posted by: Loewkyval | March 5, 2019 12:36 PM    Report this comment

Just had a tplo done on my Welsh Terrier/Poodle. This is the 4th one I've been through on 2 different dogs. It spells the end of my dog owning because of the incredible expense and the difficult recovery, this time there was a surgical infection which further complicated things.

Posted by: mjkoranda@gmail.com | March 5, 2019 11:31 AM    Report this comment

Thank you for covering this. I am currently 4 months out from my 14 month-old- Border Collie mix's luxating patella surgery. It's been a long road, and she was not diagnosed immediately, or showing any signs of pain. She would hold up the leg and skip sometimes, but never cried, licked it, etc. like you might expect. There was also ligament damage found once they got in during the operation, and it was unclear whether one caused the other. The vet's hypothesis was that her LP was the result of an injury and not congenital.

She is in every way just like you describe: a super athlete, 32 pounds and a small wiry frame, with all of the Border Collie posturing deep in her genetics to dart and leap and do everything FAST.

During the surgery process I have been disappointed in the lack of helpful information out there regarding all of the issues that I can't be facing alone: 1) working breed characteristics that lend themselves to a higher propensity for injury and what we as owners can do (anything I have found always has at least a few Border Collie owners weighing in, as well as very small breeds), 2) how to strengthen a post-op dog recovering from luxating patella surgery (or the like) and ways to avoid the same injury again in the other leg.

Appreciate your insight!

Posted by: Kesugi | February 25, 2019 4:18 PM    Report this comment

I have a soon-to-be 12 yo Border Collie mix, who has torn BOTH cruciate ligaments, the first 4-5yrs ago and the 2nd just 4mo ago. She is still recovering from the second surgery (lateral suture, which was also the procedure selected for the first tear). True to her genetics, she LOVES to herd! This includes sharp turns, fast drops and dashes. If there is no person or animal to herd, she PRETENDS that there IS!!! It is difficult to stop her unless I have her on leash at all times when she is outdoors, even in our small fenced yard. It breaks my heart to control her to such an extent. However, the alternative is another very painful injury, surgery, and extended recovery. Prevention is very important if you have a herding dog, and an aging herding dog is at VERY high risk. It may be heartbreaking for both of you, but trust me, it is better than a cruciate ligament tear.

Posted by: LifeWithDogs | February 24, 2019 7:54 PM    Report this comment

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