Cruciate ligament injury in dogs is the most common cause of hind limb lameness. Just as football players suffer cruciate ligament injuries, so do dogs – the knee is one of the weakest joints in the body.
Cruciate ligament injury in dogs can occur for serveral reasons:
- Degeneration and stretching of the cruciate ligament. This can be chronic or acute (sudden). Minor trauma to the ligament may be enough to cause complete tearing or rupture.
- Obesity or excessive weight is a risk factor for cruciate ligament injury. The ligament can become weakened due to heavy loading on the joint – this causes it to tear easily. Obesity can slow recovery time and makes the other knee more prone to injury.
- Some breeds are more susceptible to degeneration of the cruciate ligament. It is most common in medium- to large-breed dogs, often over the age of four years.
Cruciate ligament injury leads to:
- knee pain
- accumulation of fluid in the joint (effusion)
In some cases the cartilage or meniscus inside the joint may also tear.
Signs of cruciate ligament injury in dogs
Cruciate ligament disease tends to occur in two forms.
The first, chronic form, occurs in dogs with mild ongoing lameness, which may initially resolve with rest and pain relief. Eventually the lameness worsens and does not respond to pain relief.
The second, acute form, occurs in dogs with sudden onset lameness. These injuries are often more obviously painful.
In summary, signs of cruciate ligament rupture in dogs include:
- lameness (limping) in the hind limbs
- 'toe touching' at rest – the dog is not properly weight bearing but just touching the toe to the ground
- reluctance by your dog to walk or exercise
- noticeable reduction of muscle mass (muscle atrophy) around the knee
- whimpering or yelping when your dog's bearing weight on the affected leg.
How is cruciate ligament injury in dogs diagnosed?
Cruciate ligament injury can be diagnosed by your Sydney Animal Hospitals veterinarian. As affected animals are often very sore, sedation or anaesthesia is required to examine the knee thoroughly.
X-rays or radiographs are used to confirm the diagnosis, assess the viability of other joints in the leg and to plan surgery.
How are dogs with cruciate ligament injury treated?
Surgery is the mainstay of treatment. Surgery involves inspecting and cleaning the joint, removing any damaged cartilage and placing an artificial ligament.
The type of surgery performed will depend on the nature of the injury and the size of your dog. Pain relief, before and after surgery, is very important.
It is important that cruciate ligament surgery is tailored to your dog after a full veterinary examination. There is no one-size-fits-all approach to this condition.
Other important components of treatment for a dog with cruciate ligament injury, which are used in conjunction with surgery, include:
- chondroprotective agents to promote joint health
- anti-inflammatory agents to reduce inflammation in the joint and associated pain
What happens if surgery on your dog is not performed?
Very occasionally a dog that has a ruptured cruciate ligament will no longer limp – but arthritis will occur and result in lameness reappearing, usually within a few months. This lameness is usually permanent.
Some degree of arthritis will result even where surgery is performed – but as the joint is stabilised this arthritis is much less severe.
What is the Sydney Animal Hospitals approach to cruciate ligament injury?
Our veterinarians are highly skilled at diagnosing cruciate ligament injury and determining the best treatment for your pet.
As joint instability leads to worsening arthritis over time, it is important for lame dogs to be assessed as early as possible.
Why is your dog's knee so prone to injury?
The knee or stifle joint is relatively unstable because there are no interlocking bones in the joint.
Instead, the two major bones, the thigh bone (femur) and shin bone (tibia) are joined together with several ligaments.
The cranial and caudal cruciate ligaments cross over within the joint, ensuring that the bones can only move within a limited area in relation to one another. This gives the joint stability.
When one or both ligaments are torn (the cranial cruciate ligament is by far the more likely ligament to be injured), the joint becomes unstable. This results in the bones moving in an abnormal fashion in relation to one another – leading to tissue damage, inflammation, pain and of course difficulty putting weight on the limb.
Interesting facts about cruciate ligament disease in dogs
- Cruciate ligament disease appears slightly more common in middle aged, female dogs.
- In giant breeds, cruciate ligament disease tends to appear at a younger age – possibly because of more rapid degeneration of the cruciate ligament.
- In small breeds, cruciate ligament disease tends to appear at an older age – possibly because of slower degeneration of the cruciate ligament.
- It was once believed that cruciate ligament rupture occurred solely as the result of trauma to the knee. It is now believed that the majority of dogs with cruciate ligament injuries are predisposed due to inherent weakness of the cruciate ligament.
Contact Sydney Animal Hospitals for veterinary advice on treatment of your dog for cruciate ligament injury.
By Sam Haynes