Cruciate Ligament Rupture

The knee joint or stifle is basically a hinge joint that moves only backwards and forwards in one plane.  Although there are many ligaments making up the joint, the range of movement is largely controlled by two bands of fibrous tissue that cross over inside each knee joint.  These are the cruciate ligaments.  One is in front of the other, hence they are known as anterior or cranial or posterior or caudal cruciate ligaments.  They join the two major bones of the leg, the femur above and the tibia below.
We have the same anatomical structure of the knee as the dog in which the joint is known as the stifle.
Anterior cruciate ligament rupture is a common knee injury of footballers.

How does the cruciate injury occur?
Traumatic cruciate damage is caused by a twisting injury to this hinge joint.  It is most often seen in both dogs and footballers when moving at speed and suddenly changing direction so that the majority of the weight of the body is taken on the joint.  The injury usually affects only the anterior or cranial cruciate ligament.  Once stretched or torn, the joint is then unstable and weight bearing difficult if not impossible.
The injury can also occur in obese dogs just by stumbling over small objects such as a pebble whilst walking.
A chronic form of cruciate damage occurs due to weakening of the ligament, either as a result of age, disease or genetics.  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 deteriorates and subsequent ligament failure may occur.

How is it diagnosed?
Clinical signs play a large part in diagnosis.  The history with traumatic cruciate rupture is usually the dog was running in circles, suddenly pulled up and then was unable to weight bear on the affected leg.  Subsequently the dog will be seen to be standing in a very characteristic way with the affected limb just touching the ground but not bearing any weight on the limb.
During the clinical examination special tests are carried out to establish the amount of movement in the joint, the so-called “drawer sign”
The test is usually carried out under sedation or general anaesthesia.
Radiographs of the affected and the normal joints (for comparison) are often carried out at the same time.

Is other damage within the knee joint common?
Inside the stifle joint are small cartilages called menisci.  These can be damaged at the same time as the injury to the ligaments and are usually repaired during the surgical procedure.

Is operation always necessary?
Occasionally following rest and antiinflammatories healing will occur and the dog will ultimately become sound but this is often followed by the development of arthritis within the joint.  Surgery is today often the best option particularly in larger dogs.

What does surgery involve?
The aim is to restabilise the joint.  Various techniques are available, aiming to mimic the action of the cruciate ligaments.  Repair of the original ligament is rarely feasible and usually replacement using a variety of materials including skin, muscle sheath, nylon and carbon fibre is used.
Today this operation is carried out at many practices.  Alternatively you may be referred to a veterinary orthopaedist particularly if there are complications such as arthritis or if your dog is very large.  Then depending on the size, weight and age of the dog, a variety of techniques may be used which may or may not involve replacing or attempting to repair the damaged ligaments.
A technique known as tibial plateau levelling osteotomy (TPLO) is a more recent technique that has been used very successfully in certain cases.  The aim, like all techniques, is to stabilise the joint and to neutralise what is known as the cranial tibial thrust, in other words the attempt of the tibia or shin bone to move forward as the joint moves.  Variations of this technique are called tibial wedge osteotomy (TWO) and tibial tuberosity advancement (TIA).
Overall surgical success rate is more than 85%.  Thus although arthritic changes can occur post operatively, usually within 6-8 weeks after surgery your dog should be relatively sound.

Is postoperative nursing difficult?
Exercise must be strictly controlled according to instructions for the first 6-8 weeks following surgery.  Provided you are able to carry out our instructions good function should return to the limb within three months.  However irrespective of the technique used to stabilise the joint, arthritis does develop over time.  Thus as your dog gets older stiffness is often noticed.  Provided you control weight, this problem is usually no greater than that normally encountered in the knee joints of any active older dog.  If necessary the arthritic problems can be treated with an increasing number of veterinary licensed products available to help with the problem of arthritis in our pets.
More recently hydrotherapy is being used to aid recovery

Why is obesity such a problem?
As mentioned obesity can cause cruciate ligament rupture.  Recovery time in overweight dogs is often very prolonged.  During this period the other knee is very susceptible to injury since in the postoperative phase it is the main weight bearer.
We will be happy to help with weight reduction. A licensed preparation for weight reduction in dogs has been recently approved and can be considered if necessary since weight loss is, without doubt, as important as surgery in ensuring rapid return to normal function.