Cruciate Ligament Disease
What is the cranial cruciate ligament?
There are four main ligaments in the stifle (knee joint) of a dog; two outside called the collateral ligaments and two inside the joint called the cruciate ligaments. The cruciate ligament nearest the front of the joint is the cranial cruciate ligament (CCL), the equivalent to the anterior cruciate ligament or ACL in a human. The ligament attaches the femur (thigh bone) and to the tibia (shin bone), preventing the tibia from moving forward relative to the femur. It also helps to prevent over-extension and rotation. The caudal cruciate ligament is responsive for the opposing movement, principally stopping backwards movement of the tibial relative to the femur.
Why do dogs get cruciate ligament problems?
Most commonly, the ligament is injured in dogs due to a degenerative breakdown. This is in direct contrast to people where trauma is usually at fault.
Although this is a common ailment, we do not fully understand why this condition develops in dogs. We know some breeds are more commonly affected (Labradors, Rottweilers, Golden Retrievers, Boxers) and some breeds are relatively protected (greyhounds & whippets). The exact cause remains unclear. Some breeds may have conformational abnormalities which predispose to this condition (Bichon Frise or West Highland White terriers). They have similar tibial anatomy which increases pressure on the ligament. As this is a degenerative condition, we often use the term ‘cranial cruciate ligament disease’ rather than ‘cranial cruciate ligament rupture’.
What are the signs of cruciate ligament disease?
The most common sign of cranial cruciate ligament disease is hind limb lameness (limping). In dogs this can occur suddenly but in others it may develop slowly. There is a lot of variation in the degree of lameness; some dogs cannot put any weight on the leg, whereas others only have a subtle limp. In cases where both left and right ligaments are affected simultaneously, dogs won’t limp. Rather, they are prone to sitting down routinely, have trouble jumping and they often look like they are lifting themselves from the ground using their front legs only. Some dogs show stiffness after rest and others get worse after exercise.
How is cruciate ligament disease diagnosed?
A diagnosis can be straightforward if the ligament is completely ruptured and is usually confirmed on examination by an experienced orthopaedic surgeon. The most useful test is palpation of the stifle to confirm instability which identifies abnormal movement typical of ligament failure. When a partial tear is present this can be more difficult to diagnose as there is not the same degree of instability in the joint. In these cases, other tests may be required such as radiography (x-rays) and assessment under anaesthesia / sedation. Radiographs may show signs consistent with the presence of osteoarthritis which is commonly present in dogs with cranial cruciate ligament disease. In most dogs, exploratory surgery or arthroscopy (keyhole surgery) is used to confirm the ligament is damaged. The cartilage in the joint will also be assessed as meniscal (cartilage) damage can often occur along with CCL disease.
Conservative management options
This type of management uses weight control, exercise control, rehabilitation, non-steroidal anti-inflammatory drugs and dietary supplements. However, this offers a very unpredictable outcome and for this reason it is not commonly recommended in our clinic. Dogs undergoing this management may improve in the earlier phases of treatment, but longer term outcomes are often poor. Small dogs may respond better than bigger dogs, but again the outcome is unpredictable.
Many different techniques have been described for treatment of this condition and the outcomes were considered similar for a long time. However, there is a growing body of evidence which supports plateau levelling procedures in all size dogs.
Tibial Plateau Levelling Osteotomy (TPLO)
The TPLO procedure does not rely on the presence of the ligament, but instead changes the forces in the joint to create a more stable ‘platform’ when the dog is weight bearing on the leg. A semi-circular cut is made in the top of the tibia (shin bone) and the top section of bone is ‘levelled’ to improve stability in the joint. The cut bone is stabilised with a bone plate and screws. Once the bone is healed, the procedure is complete. Although the bone is cut, this is a well tolerated procedure with many dogs weight bearing on the leg within 48 hours of surgery.
At Queensland Veterinary Specialists, we are experts in this procedure, with our specialists involved in training other veterinarians in this technique. We use the highest proven quality in locking implants, using principally Synthes equipment which is an industry leader in human and veterinary orthopaedics. We can offer this technique in all size dogs, from Papillions to Great Danes with success rates exceeding 95%.
Cranial closing wedge ostectomy (CWO)
This technique also levels the top section of the tibia in a similar way to TPLO, but by removing a wedge of bone rather than using a curved cut. This was the predecessor surgery to TPLO and is occasionally used in some patients. The bone is again stabilised with a bone plate and screws.
Tibial Tuberosity Advancement (TTA)
This technique also uses a cut in the top of the tibia (shin bone), but in this case the front of the knee is ‘pushed’ forwards to change the forces in the knee.
A prosthetic ligament has now been available for many years (lateral extracapsular suture or fabello-tibial suture). Nylon is often used as the substitute ligament, secured by knotting or with a metallic crimp. However, the suture stretches or breaks over time and the patient can return to the pre-operative status in the early phases of recovery. Recently, more robust materials have been developed (Fiberwire®) which do not fatigue in the same way. These techniques may have a better outcome where the injury relates to trauma, as the knee was a ‘normal’ joint prior to injury. With genuine traumatic cranial cruciate ligament ruptures other ligaments may be affected and can be managed using the same ligament substitute material. This is known as a multi-ligamentous or a global knee injury.