Cruciate Ligament Injury

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Lilydale - Yarra Ranges Animal Hospital
484 Maroondah Hwy
VIC 3140

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03 9739 5244

Yarra Glen - Yarra Ranges Animal Hospital
28 Bell St
Yarra Glen
VIC 3775

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03 9730 1569

What is the cruciate ligament?


There are two cruciate ligaments found within the stifle (knee) joint. These are the cranial cruciate ligament and the caudal cruciate ligament – in people these are called the anterior and posterior ligaments. By far, rupture of the cranial cruciate ligament is the most common orthopaedic injury seen in our practice. The cranial cruciate ligament acts to stabilise the joint when the animal is weight bearing on the leg. When the ligament is ruptured, the stifle joint will have abnormal forwards-backwards motion when your dog places weight on the leg.



How does the injury occur?


Unlike in humans, rupture of the cruciate ligament in dogs typically occurs after a period of degeneration within the ligament, causing it to become brittle, dull and partially torn. Full rupture of the ligament then occurs with physical activity. When the ligament is torn, inflammation within the stifle joint occurs and this rapidly progresses to form the classical signs of osteoarthritis. Because of ongoing instability within the joint, other structures within the stifle are frequently damaged – we see many injured dogs with a torn meniscus within the stifle. The meniscus is a 'shock absorber' within the stifle and abnormal motion within the joint frequently causes the meniscal cartilage to tear as it is ground between the two bones of the knee joint.



What are the signs of a ruptured cruciate ligament?


 The signs of ruptured cruciate ligament vary from mild intermittent lameness – a skipping gait when your dog is running or walking – through to non weight-bearing on the leg. Sometimes dogs may suffer a partial tear of the ligament, causing osteoarthritis within the joint. These dogs may be stiff and limp when getting up from resting or after exercise. Partially torn cruciate ligaments always progress to a full rupture of the ligament and warrant treatment.

When the cruciate ligament is fully ruptured, your dog may initially take no weight or very little weight on the injured leg. This is because weight-bearing causes abnormal motion within the joint, which in turn causes acute pain. It is important to remember that your dog is limping because it hurts to place full weight on the leg. Limping is always a sign of pain.



How is this condition diagnosed?


Rupture of the cranial cruciate ligament is diagnosed by eliciting abnormal forwards-backwards motion within the stifle joint – we call this the 'cranial drawer sign'. Most commonly, due to pain and muscle stiffness, we need to perform these orthopaedic tests with your dog under sedation. Radiographs are an important part of the diagnosis also and help to rule out other conditions and assess the levels of damage secondary to cruciate ligament rupture. Radiography also assist with planning surgical treatment of the condition.


What treatment options are available?


Left untreated, the stifle joint without a functional cruciate ligament rapidly develops osteoarthritis over a period of weeks to months. Although the dog may partially bear weight on the affected leg after a few months, ongoing arthritis causes lifelong pain and lameness. Choosing not to surgically repair a cruciate ligament rupture in dogs over 5 to 10 kg is not recommended.


There are a number of treatments available for cruciate ligament rupture. Older techniques are aimed at replacing the cruciate ligament with prosthetic implants or with the dog's own tissues. The most common technique is the 'De Angelis' extracapsular suture technique wherein an 'artificial' ligament is placed outside the joint between the shin bone (the tibia) and the back of the thigh bone (the femur and another bone called the fabella). This technique is suitable for smaller patients below 10kg body weight. However, when compared with the more modern techniques, experience tells us that the recovery period is much longer for this technique. Also, bigger dogs tend to put more strain on the artificial ligament, causing a higher rate of breakage of the implant.

Modern surgical techniques for cruciate ligament injury are aimed at changing the mechanics of the knee joint such that the cruciate ligament is no longer required to stabilise the joint. Remember that without the ligament, the joint will have an abnormal forwards and backwards motion. This motion is caused by a 'downhill' slope on the top of the tibia (called the tibial plateau) which causes the femur to 'slide' down the tibial plateau when the dog puts weight on the leg. This in turn causes the tibia to move forwards and the femur to move backwards whenever the dog puts weight on the leg (this is called tibial thrust) as shown in this radiograph.


Tibial Wedge Ostectomy

At the Yarra Ranges Animal Hospital, we offer two advanced surgical procedures to modify the mechanics of the knee joint. The first surgical treatment is called a Tibial Wedge Ostectomy.

This surgery is suitable for both smaller and medium sized breeds of dogs.

The aim of this procedure is simply to flatten the top of the tibia (the tibial plateau) to eliminate tibial thrust during weight bearing. This is accomplished by removing a wedge of bone from the tibia and plating the bone together as shown in the radiograph on the left.





Tibial Plateau Levelling Osteotomy (TPLO)

The surgery recommended for larger dogs (weighing over approximately 20kg) is called a tibial plateau levelling osteotomy (TPLO). The TPLO flattens the tibial plateau by making a semi-circular cut in the tibia and rotating the top of the bone as seen in the radiograph to the right. The bone cut is stabilised with a strong bone plate and healing takes approximately 6 to 8 weeks.

TPLO is the cruciate surgery most commonly practiced by specialists in veterinary orthopaedics due to its high success rate. At the Yarra Ranges Animal Hospital, we use Synthes® 'locking' TPLO plates, which have superior manufacturing and holding properties. Please visit for more information about this procedure and the advantage of using Synthes® technology.


During both of these surgeries (T.W.O. and TPLO), the stifle joint is usually opened and the damaged ligament is removed. If the meniscal cartilages are damaged, they are also removed. The joint is closed and then either the T.W.O. or TPLO procedure is carried out. The tissues overlying the bone are sutured closed and the leg is placed in a padded bandage. Postoperative radiographs are performed to ensure that the plates, screws and wires are correctly placed.


Your dog will also receive the best medical care at our hospital. Intravenous antibiotics are given at the time of surgery and oral antibiotics are given postoperatively. For pain relief, your dog will receive intravenous opioid medications, an epidural pain relief injection and a transdermal 'fentanyl' patch. Anti-inflammatory pain relief medications are given at surgery and orally at home. Your dog will typically stay with us overnight and be discharged by your surgeon the following day.


Which surgery is best for my dog?


 This decision is made based upon your dog's size, age and radiographic appearance of the bones around the stifle. Generally speaking, most large breed dogs will benefit from the TPLO procedure, whereas the T.W.O. is best suited to dogs less than 15-20kg.


What is the expected outcome?


We expect that your dog will start placing a small amount of weight on the injured leg the day after the surgery. By 2 to 3 weeks, we expect that your dog should be placing close to 100% weight on the leg. However, this depends on the amount of osteoarthritis within the joint and the presence of a meniscal injury. Both of these conditions can slow the recovery process. The full recovery period from this surgery is at least 8 weeks while the bones heal together. During this time your dog is to be strictly rested and an exercise 'timeline' will be provided.  Regardless of the surgery performed,  we expect that your dog will require a prolonged period of rehabilitation after surgery to regain full limb function. 


What complications can occur?


Complications associated with orthopaedic surgery are divided into two groups: anaesthetic complications and surgical complications.


Anaesthetic complications are extremely rare (around 0.1% fatality), and we know that patients with risk factors such as age and other diseases are at higher risk. Therefore, your surgeon may recommend a blood profile be performed prior to surgery to lower the risk.


Surgical complications are those that occur during or after surgery. In cruciate ligament surgery, almost all complications occur postoperatively. These include:


  • Wound or joint infection. Every effort is taken to prevent infections – sterile surgical technique, intravenous antibiotic, antibiotic tablets postoperatively. However, in rare instances (about 1% of cases), infections occur despite all precautions.


  • Fluid accumulation in the wound (called a seroma). This occurs infrequently and is easily treated by either allowing the body to remove the fluid or by drainage of the fluid.


  • Implant failure. Breakage of the plates, wires and screws occurs rarely. This tends to occur almost exclusively from over-activity in the postoperative period. If the implants fail, a revision surgery may be required. It is of vital importance that you follow the rehabilitation guidelines and recommendations of your surgeon.


  • Bone fractures around plates and screws. Again, this is a rare occurrence and tends to follow boisterous activity.


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