Anomalies of the cruciate ligaments

Cruciate ligament rupture in dogs

This anomaly concerns the knee and is mainly found in dogs, but also occasionally in cats, rabbits and ferrets.

The knee or stifle is the joint between the femur on one side and the tibia on the other. This joint is partly held in place by ligaments: the collaterals on either side of the joint and the cruciate ligaments within the joint. A distinction is made between the anterior (front) and posterior (back) cruciate ligaments.

The cruciate ligaments play an essential role in the stability of the stifle, limiting torsion and, above all, preventing the tibia from moving forward. This is known as the cranial thrust force of the tibia. The anterior cruciate ligament plays the most important role and is subject to the greatest stress. When this ligament ruptures, the tibia moves forward during weight-bearing. This phenomenon can be reproduced during manipulation: it's the drawer sign, characteristic of this rupture (see video below).

Why has my dog's cruciate ligament ruptured?

In the majority of cases, a dog's cruciate ligament ruptures as part of normal activity and without violent trauma. In reality, these are so-called fatigue or wear-and-tear ruptures. It results from progressive alteration of the ligament, which wears down and eventually breaks. Family (genetic) causes are suspected, which also explains the frequency of this condition in certain breeds, such as Labrador Retrievers, Rottweilers, Newfoundlanders and Goldens Retrievers. Smaller breeds are not spared either, such as the West Highland White Terrier and the Yorkshire Terrier...

Other factors, such as chronic overweight, the presence of other abnormalities such as patella dislocation, and so-called "strained" knees with their particular anatomy, all contribute to the wear and premature rupture of these ligaments.

Because it's more a question of ligament disease than trauma, this condition usually involves the ligaments of both knees. It is therefore not uncommon for a rupture on one side to be followed by a rupture on the other within a few months.

How do I know if my dog's cruciate ligament is ruptured?

When your dog has occasional, intermittent or permanent lameness of a hind leg, it's best to have him examined by your vet. He will manipulate your dog's knee to look for the "drawer sign" characteristic of this lesion. If this sign is positive, the rupture is confirmed and no further examination is required. If the test is negative, partial or total rupture of the ligament cannot be ruled out, and further tests are recommended.

The examination of choice is then an X-ray, which can confirm a lesion in the knee, but without being able to characterize it formally. MRI is the examination of choice. It is also the first test performed in men when a rupture is suspected. Arthroscanner and arthroscopy are also indicated in certain circumstances.

How is a torn anterior cruciate ligament treated?

Surgery is recommended in the vast majority of cases. You will find full details of the different techniques on the surgical treatments page here.