What are the cruciate ligaments?
Inside the knee joint, there are two ligaments that help to hold the thigh and shin bones together, while allowing them to move relative to one another, creating a hinge joint. These ligaments are called the cruciate ligaments - together they form a ‘cross’ shape. The cranial cruciate ligament (CCL) sits at the front of the joint and prevents the shin moving forwards relative to the thigh – this is the equivalent of the anterior cruciate ligament (ACL) in humans. It is this CCL that is particularly prone to damage, with a partial or complete tear resulting in pain and instability of the knee joint. This condition is called cruciate ligament disease, and is more common in certain breeds, including Labradors, West Highland White Terriers, Rottweilers, Golden Retrievers and Boxers.
What causes cruciate ligament disease?
In humans, cruciate ligament injury is usually the result of trauma, hence ACL rupture is a fairly common injury suffered by football players. However, in dogs, cruciate ligament damage is most often the result of a degenerative condition, where fibres within the ligament weaken over time, with genuine traumatic damage (in the absence of underlying ligament degeneration) being rather uncommon. While it is quite a common condition, the cause remains elusive. We do know that certain breeds are more prone, while cruciate ligament problems are very uncommon in others e.g. sighthounds. As well as genetics, other factors are thought to also be important, including obesity, hormonal imbalance and the individual dog’s conformation (i.e. how they bare weight through their hindlimbs).
What are the symptoms of cruciate ligament injury?
The symptoms can vary from a slight limp to non-wearing lameness, but tend to include the following:
- Hindlimb lameness (mild to severe)
- Swelling of the affected knee (may be subtle)
- Difficulty getting up and lying down
- Pain in the affected leg
- Abnormal movement
When should I contact my vet?
If you are concerned that your dog is displaying any of the symptoms above, then please contact your vet.
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How is it diagnosed?
Your vet will normally perform a full orthopaedic examination, which can identify instability in the knee joint. If there is only a partial tear to the CCL then this can be more difficult to detect. Radiographs are normally taken under general anaesthetic to help confirm the diagnosis, and sometimes a camera is inserted into the knee joint to visualise the damaged ligament.
Treatment of cruciate disease
For most dogs, surgery is recommended as the treatment of choice, with more of a predictable outcome compared to medical management. If surgery is not an option, then a combination of weight control, exercise management (strict rest followed by a very gradual re-introduction), anti-inflammatory pain relief and physiotherapy can be successful, especially in smaller dogs under 15kg. This type of treatment usually takes a few weeks to a few months to work and is by no means successful in all cases.
There are various surgical treatment options available, and your vet will discuss these with you based on your dog’s size and weight. After surgery, the recovery period is normally a few weeks, during which time your dog will be given anti-inflammatory pain relief and they must be strictly rested before very gradually re-introducing exercise.
What is the outlook?
With appropriate treatment, most dogs recover well and go on to lead a normal life afterwards, although approximately one third will suffer a similar problem in the other knee. It is therefore sensible to be careful and avoid very vigorous activities such as ball chasing, skidding and jumping. It is also a good idea to keep their weight down, to avoid unnecessary pressure on the joints.