What and where are the cruciate ligaments?
There are two bands of fibrous tissue called the cruciate
ligaments in each knee joint. They join the femur and tibia
(bones above and below the knee) together so that the knee works as
a hinged joint.
They are called cruciate ligaments because they “cross over” inside
the knee joint. One ligament connects from inside to outside the
knee joint and the other outside to inside, crossing each other in
Humans have the same anatomical structure of the knee. Cruciate
ligament rupture is a common knee injury of athletes.
How does the injury occur?
The knee joint is a hinged joint and
only moves in one plane, backwards and forwards. Traumatic cruciate
damage is caused by a twisting injury to the joint. This is most
often seen in dogs and athletes when running and suddenly changing
direction so that the majority of the weight is taken on this single
joint. This injury usually affects the anterior (front) ligament.
The joint is then unstable and causes extreme pain, often resulting
The injury also occurs commonly in
obese dogs, just by stumbling over a pebble while walking.
A more chronic form of cruciate damage
can occur due to weakening of the ligaments as a result of disease.
The ligament may become stretched or partially torn and lameness may
be only slight and intermittent. With continued use of the joint,
the condition gradually gets worse until rupture occurs.
is it diagnosed?
With traumatic cruciate rupture, the
usual history is that the dog was running and suddenly stopped or
cried out and was then unable to bear weight on the affected leg.
Many pets will “toe touch” and place
only a small amount of weight on the injured leg.
During the examination, the
veterinarian will try to demonstrate a particular movement, called a
drawer sign. This indicates laxity in the knee joint. Many dogs will
require mild sedation or pain medications to perform this test.
Other diagnostic tests such as radiographs (x-rays) may also be
Other tests such as arthroscopy may be
needed to rule out other damage to the joint.
other joint damage common?
Inside the knee joint are pieces of cartilage called menisci.
Many times these cartilages are also damaged when the cruciate
ligaments rupture. They are usually repaired at the same time as the
an operation always necessary?
Dogs under 10 kgs (22 lbs.) may heal without surgery. These
patients are often restricted to cage rest for two to six weeks.
Dogs over 10 kg. (22 lbs.) require surgery to heal. Unfortunately,
most dogs will eventually require surgery to correct this painful
does surgery involve?
There are various techniques available to replace the action of the
cruciate ligaments. These surgeries most often involve the placement
of artificial ligaments along the outside of the knee joint. There
is a newer surgical technique available called tibial plateau
leveling osteotomy (TPLO) that is especially beneficial for larger,
more athletic dogs. Your veterinarian will discuss with you the best
treatment option for your pet.
post-operative care difficult?
is important that your dog have limited activity for six to eight
weeks after surgery. Provided you are able to carry out our
instructions, good function should return to the limb within three
months. Unfortunately, regardless of the technique used to stabilize
the joint, arthritis is likely to develop. As your dog ages,
stiffness is likely to develop in the joint. Weight control and
nutritional supplements such as glucosamine / chondroitin may help
reduce the risk of arthritis in your pet.
Is obesity such a problem?
can result in cruciate ligament rupture and knee arthritis. If your
dog is overweight, the recovery time will be much longer. Obesity
also increases the risk of injury to the other knee. We will be
happy to prescribe a weight reduction diet. Weight loss is as
important as surgery in ensuring rapid return to normal function.