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CRUCIATE RUPTURE

What and where are the cruciate ligaments?

There are two bands of fibrous tissue called as 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. 

Cruciate ligaments are so called because they cross over inside the joint.  There are, of course, other ligaments involved in the knee joint. 

We have the same anatomical structure of the knee.  Cruciate ligament rupture is a common knee injury of footballers.

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 footballers when moving at speed and suddenly changing direction so that the majority of the weight is taken on this single joint.  This injury usually affects the anterior (cranial) of the two crossed ligaments.  The joint is then unstable and weight bearing difficult if not impossible.

· The  injury can also occur in obese dogs, just by stumbling over a small object such as a pebble while walking.

· A more chronic form of cruciate damage can occur due to weakening of the ligaments either as a result of age or disease.  The ligament may become stretched or partially torn and lameness may be only slight and intermittent.  With unavoidable continued use of the joint the condition gradually gets worse.

How is it diagnosed?

· The initial symptoms play a part in diagnosis.   With traumatic cruciate rupture the usual story is that the dog was running in circles and suddenly pulled up and then was unable to weight  bear on the affected leg. 

· Even if this is not noticed, subsequently the dog will be seen to be standing in a very characteristic way with the affected leg just touching the ground but unable to  bear any weight on the limb.

· During the examination the vet will try to demonstrate a particular movement, called a drawer sign. This demonstrates laxity in the joint.  This can usually be done in the conscious patient.  If there is any doubt these tests may be carried out and the limb x-rayed under sedation or general anaesthesia.

· The examination may also involve other tests including arthroscopy to rule out other damage to the joint

Is other joint damage common?

Inside the joint are pieces of cartilage called menisci.  Sometimes these are also damaged at the same time as the injury.  They are usually repaired at the same time as the ligament surgery.

Is an operation always necessary?

Occasionally following joint immobilisation 'healing' will occur in that the dog will ultimately become sound but this is soon followed by the development of arthritis within the joint.  Surgery is today by far the best option particularly in larger dogs.

What does surgery involve?

Basically joint stabilisation.  There are various techniques available to aiming mimic the action of the cruciate ligaments.  They are sometimes replaced with ligaments fashioned from a variety of materials including skin, muscle sheath, nylon and carbon fibre. 

Today the operation is commonplace at many practices.  Although arthritic changes do occur post operatively, provided complications do not arise, within six to eight weeks after surgery your dog should be relatively sound.

Is post operative nursing difficult?

It is important post operatively that controlled exercise only is allowed 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.  Irrespective of the technique used to stabilise the joint, arthritis is likely to develop.  As your dog gets older, stiffness is therefore likely to develop in the joint.  However provided you control  weight  this is usually no greater than that normally encountered in the knee joints of any active, aging dog.

Is obesity such a problem?

As mentioned, obesity can result in the cruciate ligament rupture initially.  Obviously if overweight your dog's recovery time will be much longer.  It also makes the other knee very susceptible to injury particularly during the post operative phase.  We will be happy to prescribe a weight reduction diet.  Weight loss is without doubt, as important as surgery in ensuring rapid return to normal function.