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8 Symptoms of Cruciate Ligament Injuries in Dogs

8 Symptoms of Cruciate Ligament

Seeing a dog limp isn’t unusual as energetic dogs can often overdo it while they are playing. However, limping can also indicate a much more serious condition, cruciate ligament injuries, so how can you tell the difference? 

The most common signs that your dog has a cruciate ligament injury are the inability to walk or bear weight on a leg, significant pain while walking, and unusual sleeping positions. Swelling around the knee and loud clicking sounds are other key indicators of a torn ACL in dogs. 

Cruciate ligament injury in dogs is not uncommon, and it is treatable, including a range of cruciate ligament repair surgeries. Most dogs make a full recovery, so with the right treatment, it isn’t necessary to put down a dog with a torn ACL

Read up and equip yourself with knowledge about this injury so that you can identify it sooner and get your pet the help they need. 

What Is a Cruciate Ligament Injury in Dogs?

In dogs, a cruciate ligament injury (or cranial cruciate ligament (ACL) injury) refers to the rupturing of the ligament, the canine’s thigh bone and shin bone. A cruciate ligament injury can occur from either degeneration or a sudden injury and can occur in dogs of all ages. 

The cruciate ligament is the connective tissue found in the knee joint. It is what allows legs to bend. Given that the ligament is used heavily, an injury or rupture occurs when the knee degenerated over time. Ultimately, the ligament snaps like a rubber band or rope with a tear (chronic). The ligament can also rupture from sudden movement or turning of the knees (acute).

While some cruciate ligament injuries occur due to strain caused by weight and trauma, the majority of cruciate ligament injuries are due to conformational issues that some breeds of dog are genetically more predisposed to. Veterinary research suggests that cruciate ligament injury is genetic and is more common in certain breeds. 

This injury can affect both young and old dogs, though age alone isn’t enough to cause this problem. It is typically seen in 2 to 8 year old dogs since it takes time for chronic degeneration to result in a torn ligament. If caused by poor conformation and genetics, the issue will affect both knees, though only one ligament may tear. 

8 Signs of Cruciate Ligament Injury in Dogs

There is a range of symptoms that can indicate a torn ACL in dogs. Although these symptoms may indicate a different, less severe injury, multiple symptoms below often suggest a torn ACL. 

The most common signs of a cruciate ligament injury in dogs are:

1. Limping and Lameness 

Limping and lameness are the most common signs of a cruciate ligament injury. These often start at the rear leg. Your dog’s limping or lameness may be on and off, but that doesn’t mean that your dog is 100% okay, as cruciate ligament injury can sometimes get better with rest and manifest only when your dog is active.

Cruciate ligament injury often starts on one knee, and another knee will follow within two years’ time. When it starts on one knee, your dog’s gait becomes uneven, which is limping. When both knees become stiff, however, that’s lameness. It’s important to note the distinction as it can help you describe your dog’s condition to your vet. 

It is important to familiarise yourself with how your dog usually walks. There is no harm in going to the vet when something doesn’t seem right in your dog’s gait. Cruciate ligament injury, when left untreated, can become chronic osteoarthritis. This means that the tear in the knee joint will be healed over by new bones to stabilise your dog’s gait. 

2. Lethargy or Reluctance to Walk

Dogs who have cruciate ligament injury often experience lethargy or reluctance to walk due to the pain of walking. For many dogs, the unwillingness or inability to walk should immediately indicate something is wrong. 

Most dog owners walk their pets daily, which has become part of their dogs’ daily routine. However, when your dog is dealing with a torn ACL, they may simply sit and not walk at all or take a break many times when you’re already walking. If this is uncommon for your dog, you should immediately check for other symptoms of a torn ACL and consult your vet.  

3. Not Bearing Weight When Walking 

Dogs with cruciate ligament injury may not bear their weight when walking. This means that your dog is having a hard time supporting and propping themselves up when walking. This results in limping or walking on just three legs.

Not bearing weight on one of their legs is obviously abnormal in dogs and indicates something is wrong. If your dog cannot bear weight when walking or physically struggles to get up, it’s best to speak to your vet immediately. 

4. Reduced Muscle Mass Around Their Knees 

Reduced muscle mass or muscle atrophy is common when your dog has a cruciate ligament injury. Dogs prefer not to move the leg that has an injury. It is, after all, better to let it rest. However, that will result in muscle atrophy. In turn, it will weaken that leg.

Muscle atrophy is an obvious visual sign that your dog has a torn ACL. There aren’t many issues that can cause muscular atrophy in dogs, especially around the knees, so seeing reduced muscle mass near a dog’s knee is a very likely sign that they have a cruciate ligament injury. 

5. Audible or Visible Pain When Walking

It’s very uncommon to audibly hear your dog in pain while they are walking, so if you can, it may be caused by a cruciate ligament injury. If you can hear your dog yelping or see them wincing while walking, they may have torn their ACL. 

Even if you’re unsure, you should always visit a vet immediately if your pet is noticeably in pain while walking. Getting them checked immediately is vital, even if it’s not a torn ACL. No one wants their dog in that much pain, especially doing something as simple as walking around. 

6. Unusually Sitting or Sleeping Positions 

Another sign of cruciate ligament injury is sitting or sleeping with one of their legs sticking out to the side. This is a sign that their knee is causing too much pain to bend. Usually, they’re tucked in, knees bent. Seeing an abnormality in their sitting or sleeping positions can be a sign of a torn ACL.

Any dog owner will tell you that some dogs can sleep in strange positions. Often it’s cute and funny, but sometimes it can be a visual cue that something is wrong. 

7. Swelling in the Knees 

Swelling in the knees may be a later sign of the cruciate ligament injury. When their ligament is torn, there will be inflammation in the ruptured area. Scar tissues will develop over it, which can develop as knee swelling.

If you see other symptoms of cruciate ligament injury, see the vet immediately, and don’t wait to see swelling in your dog’s knees.

8. Loud Clicking in the Knees When Walking

Clicking in your dog’s knees is caused by the meniscus, which is cartilage in the knee joint prone to getting torn due to knee-related injuries. When the meniscus tears, it results in a loud clicking when walking. It’s a common side effect of a torn ACL and a strong indicator of the injury.

Meniscal tears commonly occur when an ACL has ruptured, as the joint becomes more unstable due to the tear. 

It can cause significant pain for your dog, which is why it’s essential to speak to your vet immediately when noticing the signs of an ACL rupture or a meniscal tear. Aside from checking the rupture in your dog’s ligament, you can also have them checked for a meniscal tear, as meniscal tears can be addressed at the same time as an ACL tear.

What Breeds of Dogs Are Most Affected by Cruciate Ligament Injuries? 

The dog breeds most affected by cruciate ligament injuries are Labrador Retriever, Chesapeake Bay Retriever, Saint Bernard, Akita, Rottweiler, Neapolitan Mastiff, Staffordshire Bull Terrier, Newfoundland, and German Shepherd. 

These breeds are more prone to genetically inherited poor conformation of the knee joint, which can lead to chronic degenerative changes. The dog breeds more prone to cruciate ligament injury are also those that are larger, with more muscle mass. This is because heavier dogs suffer more wear and tear in the knee joint over time. 

However, some known breeds are rarely affected by cruciate ligament injuries, such as the Basset Hound, Old English Sheepdog, Greyhound, and Dachshund.

How Are Dog Cruciate Ligament Injuries Diagnosed? 

To know whether a dog has a cruciate ligament injury, the vet will observe your dog’s gait and do a physical examination by touching the knees – especially the one that’s inflamed. In some cases, an x-ray may also be required to see any joint effusion.

An x-ray is often used to confirm whether your dog has cruciate ligament injury and to see if the other joints are suffering or may suffer the same in the near future. Usually, this is done for partial joint tears and dogs that have already developed arthritis.

An MRI scan is necessary to see the ligament in more complicated situations physically. Ultimately your vet will determine the best way to diagnose a cruciate ligament injury depending on your dog and their condition.

What Other Conditions Cause These Symptoms? 

Common conditions in dogs with similar symptoms to a cruciate ligament injury include:

  • Soft tissue-related injuries, such as joint sprains or muscle strains
  • Luxation or joint dislocation
  • Tendon rupture
  • Bone fracture
  • Knee cap displacement
  • Hip dysplasia
  • Ruptured disc
  • Panosteitis (inflammatory bone disease)
  • Osteochondrosis (cartilage disease)
  • Bone or soft tissue cancer

A vet consultation is essential to diagnose your dog with an ACL injury or alternative problem. 

How Are Cruciate Ligament Injuries Treated? 

Cruciate ligament injuries are typically treated with surgery to repair the torn ligament or correct the poor conformation of the knee, allowing the ligament to heal and preventing further degeneration. 

Non-surgical treatment options include rehabilitation therapy, medication, a dog ACL brace, or restricting activities that worsen inflammation. However, surgery is the only reliable way to resolve a torn ACL in dogs, and alternative therapies should only be used in conjunction with your vet’s recommendations.

An orthopaedic veterinary surgeon can advise you on the best technique to treat your dog’s cruciate ligament injuries. A vet may also recommend non-surgical treatments and therapies in addition to surgery. 

My Dog Has Signs of Cruciate Ligament Injury: What Should I Do? 

If you notice multiple symptoms of cruciate ligament injury, it’s essential to bring your dog to the vet as soon as possible. If your dog only shows one symptom, but it’s quite severe, like a loud clicking in isolation, it’s still worth bringing your dog to the vet. 

If your dog shows lameness or limping after an activity, have them rest for a few days. Bring your dog to the vet if the limping doesn’t go away. However, if other signs are still present after a day – especially if the pain is palpable, your dog is yelping, or there is a clicking sound in the knees – it is best to take your dog to the vet quickly.

When in doubt, it’s always best to call your veterinarian. They can advise you on whether you should be concerned and the best course of action for your dog. 

Related Questions 

How Do I Tell the Difference Between an ACL Tear and a Sprain? 

It’s hard to tell the difference between an ACL tear and a sprain, but the significance of the symptoms is the easiest way to tell them apart. If your dog is having difficulty walking, it may be a sign that it’s just a sprain where the inability to walk is often a tear. However, a vet check-up is the only way to know for sure. 

Can a Dog Walk With a Torn ACL?

Yes, a dog can still potentially walk even with a torn ACL. However, it is not advisable to let a dog continue walking on a torn ACL without treatment, whether with a knee brace or surgical intervention. A torn ACL will only worsen when stressed – such as when the dog walks or continues regular activities. 

How Can I Prevent ACL Injuries in Dogs?

To prevent cruciate ligament injuries in dogs, it’s essential to maintain a regular exercise regime and diet to help combat chronic and acute causes of cruciate ligament injury. This will help them stay fit and healthy and maintain a healthy weight, avoiding the most common causes of a torn ACL.


This article is published in good faith, for general informational and educational purposes only. Paws and More Vet Centre does not make any warranties about the ongoing completeness and reliability of this information. This article should not be used as a substitute for veterinary advice, including for diagnosis or treatment of a pet’s medical condition. Always consult a veterinary professional before making decisions on your pet’s health.