Cranial Cruciate Ligament Rupture

Knees --- we all have them. We walk on them, kneel on them, lift with them rather than with our backs. Our animal companions have knees as well; it’s the joint at the top of the rear leg where the leg leaves the body. They have a kneecap there just like we do.

Unfortunately for all of us, including our animals, the knee is not a particularly great joint. Most of our other major joints are “ball and socket” joints, where the end of one bone actually inserts into a cup on the end of the other bone.

This is a very stable and strong design. In the knee, the mostly flat end of the femur (the thighbone) sits on the flat top of the tibia (the main calf bone). Many special ligaments and cartilage structures also make up the knee joint, and their job is to hold the two flat ends of bone together. The strength and stability provided is good from front to back, but somewhat poor from side to side.

For those of us who watch or play sports, the frequency of ACL injuries in athletes is well known. These injuries occur when the knee is hit on the side, or when the knee is twisted so that a sideways force is applied. These same kinds of forces cause a similar injury in dogs (and the occasional cat). In our small animal companions, any knee injury is of concern because their knees are always at work; since their knee is bent up under them, the ligaments supporting the joint are always holding weight except when they sit or lie down.

Just like our joints, our animals’ joints can sustain a variety of injuries. Animals can strain and sprain tendons and ligaments, and they can partially and completely tear these structures. It can be difficult to differentiate these injuries, and diagnosis often requires anesthesia, palpation and x-rays. In the case of lesser injuries to the knee, strict rest and anti-inflammatory drugs can allow for healing. In the case of cruciate tears, surgery is necessary to stabilize the joint, relieve pain, and enable the animal to walk and run. There are different surgical options, and we would be happy to discuss them with you if needed.

Different surgical options are available for animals; both are aimed at stabilizing the joint. One is typically done by board-certified surgeons at specialty practices, and involves cutting off the top of the tibia, repositioning it, and plating it in a new position. The other surgery involves passing a stabilizing line from the front of the tibia around the back of the knee. This surgery is often done in regular veterinary practices; in certain cases we can do this surgery here at Rose Hill. We would be happy to discuss the various options with you if needed.

If your dog (or cat) is limping, you should have the lameness checked. It is a very good idea to enforce strict rest in your animal before you get to the vet. Our animals are often not very good at resting themselves! They can cause further injury by racing around on legs that have already sustained a slight injury.