Ruptured Cranial Cruciate Ligament

Before We Get Started

Dr Geoff Golovsky does all the orthopaedic/cruciate surgeries at Vet HQ. Dr Geoff gained his memberships to the Australian College of Veterinary Surgeons in 2008. In everyday terms, this is the equivalent to getting on a specialist training program in human medicine, ‘a registrar’. Dr Geoff also completed the requirements for his Certificate in Small Animal Surgery in the UK. When he was training, he spent three years working under a specialist surgeon. He has since, and continues to, complete many further educational training opportunities on orthopaedic and soft tissue surgery. Dr Geoff, however, prefers general practice to specialisation. As such, he has combined his two passions and now concentrates on surgery for his general practice.

With respect to cruciates, Dr Geoff has been performing De-Angelis lateral stabilisations for 20 years. In 2009 he travelled to the UK to learn the Tibial Plateau Levelling (TTA) technique from the surgeons who designed it. Subsequently, Dr Geoff was one of the first in Australian general practice performing TTA’s. He continues to undertake further training on TTA techniques and always keeps his protocols up to date depending on current thoughts and the latest research.

The Basics

The knee is a fairly complicated joint. It consists of the femur above, the tibia below, the kneecap (or patella) in front, and the bean-like fabellae behind. Pieces of cartilage called the medial and lateral menisci fit between the femur and tibia like cushions. Assorted ligaments hold everything together and allow the knee to bend the way it should and prevent it from bending the way it shouldn’t.

There are two cruciate ligaments that cross inside the knee joint: the anterior (or, more correctly in animals, cranial) cruciate and the posterior (or, more correctly in animals, the caudal) cruciate. They are named for the side of the knee (front or back) where their lower attachment is found. The anterior cruciate ligament prevents the tibia from slipping forward out from under the femur.

People stand vertically and therefore when walking or even jogging, the cranial cruciate is not under load. Animals, however, stand constantly in load, at approximately 20 degrees. This is like us wearing ski boots. If you know the sensation of removing ski boots at the end of the day, you understand the load that dogs carry on their knees all the time.

Finding the Rupture

The ruptured cruciate ligament is the most common knee injury in dogs. In fact, the chances are that any dog with sudden rear leg lameness has a ruptured anterior cruciate ligament as opposed to anything else.

The history usually involves a rear leg that is suddenly so sore that the dog can hardly bear weight on it. If left alone, the leg will appear to improve over the course of a week or two, but the knee will be notably swollen, and arthritis will set in quickly. Dogs are seen by the veterinarian in either the acute stage (shortly after the injury) or in the chronic stage (weeks or months later).

It is not uncommon for dogs to have an episode of lameness that then resolves and recurs on a regular basis over time. The ‘partial cruciate’ can be harder to diagnose, but invariably at some point all partial tears in animals become full tears because of the angle of standing. The key to the diagnosis of the ruptured cruciate ligament is the demonstration of an abnormal knee motion called a drawer sign. It is not possible for a normal knee to show this sign.

The Drawer Sign

The veterinarian stabilises the position of the femur with one hand and manipulates the tibia with the other hand. If the tibia moves forward like a drawer being opened, the cruciate ligament is ruptured. Another test that can be used, is the tibial compression test. This is where the veterinarian stabilises the femur with one hand and flexes the ankle with the other hand. If the ligament is ruptured, again the tibia moves abnormally forward.

If the rupture occurred some time ago, there will be swelling on the side of the knee joint that faces the opposing leg. This is called a medial buttress and is a sign that arthritis has progressed.

It is not unusual for animals to be tense or frightened at the veterinary clinic. Tense muscles can temporarily stabilize the knee, preventing demonstration of the drawer sign during examination. Often sedation is needed to get a good evaluation of the knee. This is especially true with larger dogs. Eliciting a drawer sign can be difficult if the ligament is only partially ruptured. Partial disease is often progressive so initially there may be no evidence but 1-3 months down the line it may become obvious there is a cruciate rupture.

Since arthritis can set in relatively quickly after a cruciate ligament rupture, radiographs (x-rays) to assess arthritis are helpful. A further reason for radiographs is that occasionally, when the cruciate ligament tears, a piece of bone where the ligament attaches to the tibia also breaks off. This will require repair and the surgeon will need to know about it before beginning surgery. Arthritis that has set in prior to surgery limits the extent of the recovery after surgery. Although surgery is still required to slow or even curtail further arthritis development.

How A Cruciate Rupture Happens

There are several clinical scenarios in relation to ruptured cruciates. One is a young, athletic dog playing roughly, who takes a bad step and injures the knee while playing. This is usually a sudden lameness in a young, large-breed dog. A recent study identified the following breeds as being particularly at risk for this phenomenon: Neapolitan Mastiff, Newfoundland, Akita, St. Bernard, Rottweiler, Golden Retriever, Labrador, and American Staffordshire Terrier.

On the other hand, an older large dog, especially if overweight, can have weakened ligaments and slowly stretch or partially tear them. The partial rupture may be detected, or the problem may not become apparent until the ligament breaks completely. In this type of patient, stepping down off the bed or a small jump can be all it takes to break the ligament. The lameness may be acute but have features of more chronic joint disease, or the lameness may simply be a more gradual/chronic problem. Larger, overweight dogs that rupture one cruciate ligament, frequently rupture the other one within a year’s time. An owner should be prepared for another surgery in this time frame.

What Happens if the Cruciate Rupture is Not Surgically Repaired

Without an intact cruciate ligament, the knee is unstable. Wear between the bones and meniscal cartilage becomes abnormal, and the joint begins to develop degenerative changes. Bone spurs, called osteophytes develop, resulting in chronic pain and loss of joint motion. This process can be arrested by surgery but cannot be reversed.

Osteophytes are evident as soon as 1 to 3 weeks after the rupture in some patients. This kind of joint disease is substantially more difficult for a large breed dog to bear, though all dogs will ultimately show degenerative changes. Typically, after several weeks from the time of the acute injury, the dog may appear to get better but is not likely to return to normal permanently.

An example of a knee with moderate arthritis. There is roughening of the bone where all the red arrows are and there is ‘fluffiness’ between the two bones that indicates excessive joint fluid production.

Surgical Options

There are many different surgical repair techniques commonly used. It should be noted that no technique is perfect. In the human world, when they repair a cruciate, doctors expect the knee to be stronger post operatively. They also expect minimal progression of arthritis.

In dogs, no matter what we do, we get progression of arthritis. However, surgery is essential to get your dog functioning back to ‘normal’ and to reduce the chance of the cruciate on the other side going. Dogs have a greater than 50% chance of rupturing their other cruciate ligament. See below for details outlining relevant surgical procedures.

De-Angelis, Extracapsular Repair


Extracapsular repair with the ligament highlighted in white to demonstrate position. Usually a thick suture is used rather than wire. The wire shows where the suture would be placed around the knee.

An X-ray of what we actually do. The strong ligament fibre we use is held together with stainless steel crimps and the fibre is passed through a bone tunnel, through a button and back.

This procedure is currently favoured in small animals. The surgery can be performed in a relatively shorter time than the other procedures. The knee joint is opened and inspected. The torn or partly torn cruciate ligament is removed. If the meniscus is torn, the damaged portion is removed. A large, strong suture is passed around the fabella, behind the knee and through a hole drilled in the front of the tibia. This tightens the joint to prevent the drawer motion, effectively taking over the job of the cruciate ligament.

We recommend this procedure in dogs less than 10Kg of weight and all cats. Typically, the dog may carry the leg up for a good 2 weeks after surgery but will increase knee use over the next 2 months, eventually returning to normal. Typically, the dog will require 8 weeks of exercise restriction after surgery (no running, only outside on a leash, including the backyard).

Tibial Tuberosity Advancement (TTA)

The TTA technique changes the angle of the knee by cutting and advancing a small part of the bone that has the attachment of the patella tendon.

The idea is that when the cruciate ligament is torn, the tibial plateau (the top of the tibia) and the patella ligament should be repositioned at 90 degrees to one another to combat the sheer force generated as the dog walks. To make this happen, the tibial tuberosity (front of the tibia where the patella ligament attaches) is separated and anchored in its new position by a titanium or steel cage, fork and plate. Bone grafts are used to assist healing.

This procedure was developed in 2002 at the University of Zurich and since then hundreds of thousands of patients worldwide have had this surgery. At Vet HQ, we have the experience and technology to perform these surgeries in all dogs greater than 10kg of weight. We perform approximately one per week.

The patient’s activity must be restricted, and post-operative confinement is a must with gradually increased activity over 3 to 4 months. Most dogs can return to normal activity by 4 months after surgery.

This technique recently has been shown to be biodynamically superior than the TPLO (see later) although this is a controversial topic. We perform this procedure at Vet HQ.


This is a lateral x-ray of an immediate post operative leg indicating where the implants are positioned. The implants are a combination of titanium and stainless steel.

This is front to back x-ray showing the same thing.

Tibial Plateau Leveling Osteotomy (TPLO)

This procedure uses a similar approach to the TTA and addresses the long-term standing angle issue. With this surgery, the tibia is cut and rotated in such a way that the natural weight bearing of the dog actually stabilises the knee joint. As per the TTA, the knee joint still must be opened and damaged meniscus removed. The cruciate ligament remnants may or may not be removed depending on the degree of damage.

This surgery is complex and involves special training and has potentially a higher complication rate than the above TTA. Many radiographs are necessary to calculate the angle of the osteotomy (the cut in the tibia).

At this time, the TPLO and TTA are considered by many experts, the best way to repair a cruciate ligament rupture, regardless of the size of the dog and is especially appropriate for dogs over 20kg. Typically, most dogs are touching their toes to the ground by 10 days after surgery, although it can take up to 3 weeks. As with other techniques, 8 weeks of exercise restriction is needed. Full function is generally achieved 3 to 4 months after surgery and the dog may return to normal activity.

Meniscal Injury

We mentioned the meniscus as part of the knee joint. The bones of all joints are capped with cartilage to provide a slippery surface where the bones contact each other (if the bones contact each other without cartilage, they grind each other down). In addition to these cartilage caps, the stifle joint has two “blocks” of cartilage in-between the bones. These blocks are called the menisci and serve to distribute approximately 65% of the compressive load delivered to the knee.

When the crucial ligament ruptures, the medial (on the inner side of the knee) meniscus frequently tears and must either be removed, partly removed or ideally repaired. This is generally done at the time of cruciate ligament surgery.

Pets with meniscal damage may have an audible clicking sound when they walk or when the knee is examined, but for a definitive diagnosis the menisci must actually be inspected during surgery. It is difficult to access the menisci and thus repairing a tear in the meniscus is problematic; furthermore, poor blood supply to the menisci also makes good healing less likely. For these reasons, removal of the damaged portion of the meniscus is the most common surgical choice. This leaves some meniscus behind to distribute the compression load on the knee but removes the painful, ineffective portion.

At Vet HQ we remove the damaged section and perform a meniscal release if it is indicated. If the meniscus is not damaged, we prefer to leave the meniscus, as it provides significant protection to the joint and reduces ongoing osteoarthritis. There is a small 3-6% chance of late meniscal damage after surgery. If this occurs, a small surgery is required to remove the meniscus. We feel it is better, in a small number of cases, to have to repeat surgery than to remove the meniscus in all cases (which some surgeons do) and loose the protection it offers.

General Rehabilitation after Surgery

Rehabilitation following the extracapsular repair and TTA’s is very similar. We work off a rule of 4 weeks with minimal exercise, minimal movement and cage rest. During this time there is lots of icing, massage and passive range of motion exercises.

From weeks 5-8 we slowly return to normal ON LEASH exercise and from 9-12 weeks we return to normal in the house and in the park including off leash exercise. Our expectation is that all dogs are essentially back to normal by 12 weeks. For more details on rehab we have a post op rehab guideline hand out and a physiotherapy hand out that we will go through with you after surgery. We also have several You Tube videos on this on our You Tube channel.

It is important that your pets do not experience pain. We keep them in hospital until they are pain controlled and you administer a variety of medications at home to control pain. During the rehab process, let your pet guide you. Avoid twisting the leg. After the stitches or staples are out (or after the skin has healed in about 10-14 days), water treadmill exercise can be used if a facility is available. This requires strict observation and, if possible, the patient should wear a life jacket. Walking uphill or on stairs is helpful for strengthening the back legs but no running, jumping or other “explosive” type exercise should be performed for a full three months after surgery.

What If The Rupture Isn’t Discovered For Years And Joint Disease Is Already Advanced?

Medical management for arthritis is complex and ongoing. We will determine if surgery is the best option for you. If we don’t think it is going to be beneficial, and for all cases where arthritis management will be part of ongoing life, we recommend all or a combination of the following treatments that we perform at Vet HQ.

  • Weight loss
  • Green lipped mussel products such as Antinol
  • Pentosan polysulphate injections weekly for four weeks every year
  • Pentosan Injections monthly to quarterly if required
  • Hills J/D prescription food
  • Massage and acupuncture/dry needling

Referral services that may be applicable:

  • Laser therapy
  • Physiotherapy
  • Hydrotherapy

If you have any questions, please do not hesitate to ask one of the veterinarians at the time of consult.