What Causes Dogs To Tear Their Cruciate Ligament?

Tearing or rupturing a cruciate ligament accounts for around 20% of the leg problems in dogs. That’s a massive risk, especially when you look at what’s needed to fix them.

That risk isn’t evenly spread either. Some dogs are much more likely to tear an ACL than others. Two of those four risks are under your control.

Risk Factors For ACL Injuries In Dogs

Let’s take a tour through what we know. I’ll start with the risks you can’t control.

1. Breed

Every vet knows that some breeds are more likely to ‘do a cruciate’ than others. We don’t understand the mechanism, but it’s probably related to the shape of their joints and their tendency for arthritis.

This is a good time to explode a particular myth about dog ACLs. They almost never tear during sporting activities. Most dog cruciate ligaments which rupture have been slowly degenerating for some time until they finally go ‘pop’. This might happen on a walk or a trip to the toilet.

When many owners of affected dogs look back, their dog has been getting little twinges for some time before the failure occurs. The reason for this is that there has been something wrong with the joint for a while. It’s rare for me to operate on a cruciate ligament and not to see pre-existing arthritis for example.

Breeds At Higher Risk Of A Torn ACL

So what are those breeds? The following table comes from a recent Swedish study. Although it’s missing the common Australian breeds, my impressions are that these breeds are rarely affected anyway.

BreedRelative risk
American Bulldog7.18
Dogue de Bordeaux6.89
English Bulldog6.5
Chow Chow6.24
Cane Corso4.99
Cairn Terrier4.48
Bichon Frise3.98
Staffordshire Bull Terrier3.78
Bernese Mountain Dog3.44
American Staffordshire Terrier3
American Cocker Spaniel2.86
Yorkshire Terrier2.6
Border Terrier2.13
Labrador Retriever1.48
Golden Retrievers have also been included in other studies. A relative risk = 1 means the dog is at the same risk as the average for the population

2. Age

The average age for a dog to rupture a cruciate ligament is seven. In other words, they are neither young nor old. But this average hides important differences between breeds too.

There are those that go early.

Dog Breeds With Early CLRAge at first CLR
English Bulldog2.65
French Bulldog2.67
Cane Corso2.68
American Staffordshire Terrier3.56
American Bulldog3.56
Dogue de Bordeaux3.92
Staffordshire Bull Terrier4.75
CLR = cruciate ligament rupture

And those that go late.

Dog Breeds With Late CLRAge at first CLR
Jack Russell Terrier8.44
Bichon Frise8.81
Border Terrier9.37
Miniature and Toy Poodle9.38
Cairn Terrier9.41
Medium Poodle9.59
West Highland White Terrier11.1
Tibetan Spaniel11.3

Of course, there’s nothing you can do about this once you’ve chosen a dog. The next two are where you can really make a difference.

3. Body Condition

Excess body condition has a significant effect on the risk of cruciate rupture. In the study referenced below, a dog with a torn ACL was around twice as likely to be overweight as an average member of the same breed.

It’s hard to say what this means for the risk of tearing the ACL in the first place, but it also probably also doubles.

Body condition is not the same as body weight. Within a breed, dogs of different sizes but the same body condition do not have a different risk.

4. Desexing Age

The most recently understood risk factor is the age at which a dog is desexed or neutered. Neutering itself does not increase the risk as long as the right time is chosen.

The big message to come out of 2020 is that this risk is unpredictable, and varies greatly between dogs (those pesky breeds again!).

You can imagine my mood when I read the paper and realised I had to write 40 web pages to properly explain the risk for each breed. Let’s just say that you get to reap the benefit and I’m glad it’s over.

There are also some general guidelines for dogs of different sizes. Personally, I would also delay desexing for any of the higher risk breeds shown above.

What About Exercise?

What doesn’t increase the risk is the type of activity of your dog. This fits with my experience; we almost never see Greyhounds with ruptured cruciates for example.

When a dog tears their ACL it’s usually no one’s fault. Not even their own!

If this has happened to your dog, don’t despair. Repair techniques only get better, and after the recovery, a normal life awaits.

You might also like: How To Fix A Torn ACL In Dogs


Engdahl, K., Emanuelson, U., Höglund, O., Bergström, A., & Hanson, J. (2021). The epidemiology of cruciate ligament rupture in an insured Swedish dog population. Scientific reports, 11(1), 1-11

Lampman, T. J., Lund, E. M., & Lipowitz, A. J. (2003). Cranial cruciate disease: current status of diagnosis, surgery, and risk for disease. Veterinary and Comparative Orthopaedics and Traumatology, 16(03), 122-126

Terhaar, H. M., Muir, P., Baker, L. A., Binversie, E. E., Chi, J., & Sample, S. J. (2020). Contribution of habitual activity to cruciate ligament rupture in Labrador Retrievers. Veterinary and comparative orthopaedics and traumatology: VCOT, 33(2), 82

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By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. Meet his team here.