Thursday, August 9, 2018

Hanging by a Thread? Stabilizing Forces in the Canine Stiffle

A [cranial] cruciate ligament (CCL/ACL) tear is the most common knee injury in dogs. Is the knee anatomy to blame?

Is the fate of the knee literally hanging by a thread of the cruciate ligament?


Dog CCL Injuries: Hanging by a Thread? Stabilizing Forces in the Canine Stiffle

If you look at the anatomy of the bones, the knee joint does look like the most unstable conformation imaginable with the tip of the femur literally just balancing on the top of the tibia. It appears to be the equivalent of a person tiptoeing on a tightrope.

Now imagine that person being kept from falling off by a tiny rubber band. Ugh. Ligaments are tough but seriously? Did mother nature pull an evil prank? And if that's so, how did wolves, dependent on being able to hunt down prey, made it through the evolution to this day?

Did we screw this up through breeding?


Some argue that the tibial plateau angle--how sloped the top of the tibia is--is one of the primary determining factors. That would make sense. It's easier to fall off an incline than off a level ground. To fall on the level ground, you'd either need to be drunk or amazingly clumsy.

A study comparing the tibial plateau angles (TPA) in dogs with or without CCL injuries and wolves, though, didn't find much of a difference. (Source: University of Zurich)

Taking a look at the stifle anatomy, shouldn't the CCL provide only minor corrections rather than holding the whole thing together? And if that is the case, what else needs to fail for the ligament to tear?

The function of the CCL


There are two ligaments within the stifle; cranial, and caudal. One serves to prevent the femur from thrusting forward, the other prevents it from sliding backward. Shouldn't the patellar ligament help the CCL with the job? It surely is much bigger?

The canine stifle consists of more than just a couple of bones and a couple of ligaments. What about other tissues such as the cartilage or synovium? What about hind leg muscles?


In most cases, CCL injury is not a question of a perfectly healthy CCL in a perfectly healthy knee getting torn. It can happen, but it's actually quite rare.

More often, a cruciate injury is a result of cruciate disease rather than a sudden trauma.


Muscle weakness and dysfunction, misalignments and instabilities, distorted joint contact areas and pressures, conformational changes, as well as biologic components including inflammation, degeneration, and impaired tissue regeneration and maintenance all play their role.

What comes first, poorly ligament in an otherwise normal stifle or an abnormal function of the stifle? Or is it a combination of both?

Nobody knows for sure.


I figure that evolution would not result in faulty parts because, without a correction, a species would not survive. The original engineering then must be adequate, and something got screwed up due to our [human] influence.

The knee stability involves a number of players.


The stifle stabilizers include not only the cruciate ligaments but collateral ligaments, menisci, joint capsule, muscle and tendon components. In other words, if things go wrong, the CCL cannot be the only one to blame. That just wouldn't make sense. You wouldn't use a paddle to steer a cruise ship.

Hormonal and metabolic issues have recently been implicated in cruciate disease. Obesity, early spay or neuter, hypothyroidism all have their involvement.

Understanding the problem helps with prevention and treatment.


It would seem that focusing too much on the ligament alone misses the bigger picture. If the button on your pants comes off, you can focus on that alone and merely replace it. You might, however, miss the point that the pants no longer fit and you either need to lose some weight or get a new pair of pants.

To me, this says that simply trying to replace the stabilizing force of the CCL might be an incomplete answer to the problem. Which would also explain why surgery alone, whichever one you might choose, will not restore your dog's leg to full function. Physical therapy, medical and nutritional support are an inseparable part of the treatment.


Further reading:
The Pathophysiology and Medical and Surgical Treatment of Cruciate Ligament Disease
Don't Forget The Physical Therapy


Related articles:
Dog Knee Injuries: My Two Cents on Cora-based Leveling Osteotomy (CBLO) Repair
What Is That Limp?
Talk To Me About Dog ACL/CCL Injuries (I do need to update this one)
Triple Tibial Osteotomy (TTO)
Simitri Stable in Stride
Is There Such a Thing as a False Drawer Sign?
Preventing ACL Injuries in Dogs
Preventing ACL/CCL Tears Part I
Preventing ACL/CCL Tears Part II (All or None or Partial) 
Full Cruciate Ligament Tears
Ruptured Cruciate Ligaments and Early Spay and Neuter
ACL Injuries in Dogs: Non-Surgical Alternatives
Platelet-Rich Plasma (PRP) Treatment for Cookie's Bad Knee(s)
Cruciate Ligament (ACL/CCL) Surgery Post-Op Care Example Plan
Surviving the Post-Op After Your Dog's ACL/CCL Surgery

29 comments

  1. I was not aware that CCL/ACL injuries are the most common knee injuries in dogs. And although I have heard about this injury-in humans as well, I did not quite fully understand it, but now it makes more sense. Great topic, well put.

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    1. Oh yes, very common, unfortunately.

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  2. Wow that is scary to think the knee could literally be hanging by a thread. I do like your analogy of the missing button and agree, you have to understand the problem and all its components in order to come up with a treatment and management plan. My dog Jack became paralysed quite suddenly a couple of years ago because a disc exploded in his back. Thankfully he recovered well from spinal surgery, and although it's not the issue you're talking about, the theme of it not being one thing got me thinking the same is true in his case. Thanks for another very informative post, I always learn so much from you.

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    1. Thank you, Hindy. Yeah, I like making analogies :-)

      Fortunately, many dogs recover from disc issues quite well.

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  3. Very informative post! I've heard of these knee injuries before but, until now, didn't know all that much about them.

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  4. My weekly medical lesson but am blessed as this week I took Layla for her bi-annual check up and the vet is very happy with her health so am a happy Mom

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    Replies
    1. Yay for Layla. I'm very happy to hear that.

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  5. I've heard about this often. Not fun for the dogs or the humans that have to pay for it or manage the recovery.

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    Replies
    1. Definitely not fun; 6 months out of the dog's life.

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  6. I'm amazed at how common CCL/ACL tears are in dogs, now I can see why. Thanks for the inside scoop!
    Love & Biscuits,
    Dogs Luv Us and We Luv Them

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    1. It seems to me that the main causes are early spay/neuter, obesity, and under-active thyroid.

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  7. My friend's dog had to have knee surgery. It was a stressful time for both her and her baby. Very informative post!

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    Replies
    1. It definitely is. Been through that twice. The second time is easier on everybody somehow.

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  8. Even reading about this is enough to make me wince in pain.

    As I read I realised this has expensive written all over it! Thank heavens for dog insurance!

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    1. I gets expensive though there are problems which are much costlier. Having an insurance is the best thing to have. That way one cam make decision based on what is the best thing to do and not based on what they can afford.

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  9. I tore my ligaments (pcl and acl then later mcl) in a motor bike accident in Bali as a teen ager then playing tennis). So painful and never healed well. I did know about arthritis but not realize that these injuries were so common in dogs or understand the structural issues.

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  10. I don't have a dog however I like the analogy you made about the button and the pants. Get to the source of the issue vs. only treating it with surgery. I guess all factors need to be taken into consideration besides genes; nutrition, activity, supplements, etc. Interesting post. I never knew.

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    1. Thank you, Kamira, I'm glad somebody likes my analogies :-) Surgery is often the best option but by itself is not likely to make things right.

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  11. It is scary to think that just a small thread compared to the rest of the body is holding the need to gather. I’ve seen a few issues with dogs by watching some of the TV shows on animal planet. I also know how a small tear can impact the way you walk in the rest of your body because I have a torn meniscus.

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    1. Well, it doesn't. That's the point I was trying to make. It's mean for minor corrections to a forward thrust. That's why there must be way more to the picture than meets the eye.

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  12. I always thought that CCL tears were due to an injury, I had no idea that it could be related to disease and obesity. Theo was quite overweight when we adopted him 5 years ago, but has maintained a healthy weight for the last 4. Hopefully, he won't have any issues with knees.

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    1. It can happen as an injury to a perfectly healthy ligament but it is quite rare. What usually happens that there is progressive weakening and wear which eventually won't handle load it normally should.

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  13. These small ligaments help explain why it is so easy to get a torn CCL. One of my cockers had several tears in both of his back legs. He was pretty old, so it wasn't due to over exertion, except sometimes he lunged at other dogs - causing the tear.

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    1. A small lunge can be all it takes to bust a weak ligament. They are small but ligament tissue is normally very strong. As well as I believe there needs to be a breakdown in the other stabilizing aspects for this to happen.

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  14. It's more of an issue with bigger dogs if I remember correctly right? Is it just more wear and tear on their joints? Small dogs seem to have more issues with patellas.

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    1. It is mostly an issue with bigger dogs, yes. Though small dogs can get their CCL(s) tear also. It's a multifactorial problem. More than one thing has to fail.

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  15. I've known a couple of people that have gone through this with their dogs. Costly and very difficult to keep the dogs settled enough to recover. Nasty injury.

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    1. Yes. Not cheap, not fun, not easy. Been there, done that.

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