What is the ACL or CCL? (Cranial Cruciate Ligament)

The dog knee (stifle) is not all that different from a human knee.  There are four ligaments primarily responsible for stability of the stifle – the cranial cruciate, caudal cruciate, medial collateral, and lateral collateral.   The dog stifle differs from the human knee in that the top of a dog tibia has a more significant slope (tibial plateau slope/angle) than that of a human knee.  The cranial cruciate ligament (CrCL/CCL, equivalent to the anterior cruciate ligament or ACL in people) is responsible for limiting hyperextension of the stifle, limiting internal rotation of the tibia (shin bone) in relationship to the femur (thigh bone), and to prevent forward sliding/drawer motion of the tibia in relationship to the femur.

What causes the ACL or CCL to tear?

Cranial cruciate ligament rupture (CrCLR) is the most common orthopedic condition in dogs. Cranial cruciate ligament ruptures in dogs are different than ACL injuries in most people.  Whereas trauma is a common cause of ACL tears in people, CrCLR in dogs is typically degenerative in nature. Some proposed predisposing factors for cruciate injuries in dogs include genetics, obesity and fitness level, early neutering, tibial plateau slope, immune-mediated disease, and bacterial presence within the joint.  Female young to middle-aged large breed dogs are at greatest risk for tearing their cranial cruciate ligament, though any dog can develop a CrCLR.

Though the underlying cause of disease may be different in each dog, the anatomy of the joint plays a role in the continued breakdown of the ligament.  Due to the slope of the tibial plateau, the cranial cruciate ligament of the dog is always under stress during weight bearing, as it attempts to keep the femur and the tibia in appropriate alignment.  Once the integrity of the ligament is compromised to a certain degree the tibia begins to move forward in relationship to the femur during weight bearing. This instability is partly responsible for the pain present in dogs with this injury the primary reason why treatment options for ACL tears in humans and CrCLR in dogs may be different.  As the cruciate ligament tears, inflammatory changes are also taking place in the joint including synovitis (inflammation of the lining of the joint), effusion (swelling in the joint), and arthritis formation.  In most patients, once this degenerative process begins, the ligament will go on to a complete tear. Approximately half of all patients that go to surgery for repair of a CrCLR will still have a portion of the ligament left intact.

My dog is limping, how does my veterinarian know the Cranial Cruciate Ligament is torn?

Clinical signs of early (partial) CrCLR may include an acute onset hindlimb lameness following activity (can be weight bearing or non-weight bearing) that improves with time and is followed by intermittent stiffness or mild to moderate lameness following heavy activity.  It is very common to hear a history of a waxing and waning lameness.  As the disease advances and the ligament progressively tears, the lameness may become more consistent. Acute complete tears may initially result in a non-weight bearing lameness on the limb, but as time goes on the dog will start to use the limb.  Instability in the joint associated with CrCLR can lead to injury of the meniscus. Injury of the meniscus can be extremely painful for pets and may, for a period of time, lead to a non-weight bearing lameness.

There are multiple tests your veterinarian can perform to help diagnose a cranial cruciate ligament tear.  One of the first signs present prior to instability may be pain with full extension (hyperextension) of the knee.  Once the ligament tears to a certain degree the tibia can be manually manipulated to show instability in what is called the “cranial drawer test” in which the tibia can be moved forward in relationship to the femur.  Another sign, referred to as tibial thrust, may be elicited as well.  With this test, weight bearing is mimicked and the front of the tibia can be noted to be pushing forward in relationship to the femur.

Other signs that may be noted on physical exam include detection of effusion (swelling) within the joint and scar tissue formation around the knee.  This scar tissue is the body’s natural response to try and stabilize an unstable joint.  Long-term this scar tissue leads to a decreased range of motion in the knee.

Though the cranial cruciate ligament is not visible on an x-ray, radiographs can help confirm a diagnosis of a CrCLR by detection of changes that occur in the joint following this injury.  These changes may include effusion (excess fluid in the stifle) and arthritis.  Radiographs can also help rule out other concurrent injuries. Approximately half of all patients that go to surgery for repair of a CrCLR will still have a portion of the ligament left intact.

What are the treatment options for my dog?

As with many diseases, there are both medical and surgical treatment options for patients suffering from CrCLR.  The choice to pursue surgical management is typically based on patient size, the stage of disease, the amount of instability present, the expectations you have for your pets activity level/quality of life, and the presence of any other concurrent medical conditions (severe heart disease, uncontrolled hormonal disease, cancer, etc).

Medical management consists of:

1.)  Pain management with anti-inflammatories and/or pain medications

2.)  Weight management

3.)  Exercise modification

4.)  Joint supplements

Often when a diagnosis of CrCLR has been made, patients are painful and gingerly using the affected limb.  Pain management is an important aspect of treatment in the early stages of medical management and will likely be required intermittently throughout life.  Weight management and exercise modification are likely the most important things you can do to medically manage a patient with a CrCLR.  Obesity has been found to quadruple the risk of CrCLR and weight loss alone may decrease the necessity for surgery in some overweight patients.  Scoring systems have been developed to help assess a patient’s body condition.  These scoring systems have an “ideal” weight for patients.  It is recommended that patients with orthopedic disease, such as hip dysplasia and CrCLR, be maintained slightly under this ideal weight.  Studies have shown that obese patients have an earlier onset and a faster progression of osteoarthritis.  Keeping a patient skinny decreases forces applied to joints, decreases systemic inflammation and may delay or eliminate the need for surgery.  Along with weight management, maintaining a baseline level of fitness is paramount in the treatment of osteoarthritis.   It is best to avoid ‘weekend-warrior’ type of exercise (going for a 3 hour hike once a month).  Multiple short walks are better than one long one.  Taking your pet on controlled daily walks is ideal, starting with short durations and then slightly increasing as they become tolerated.  High-impact activities such as Frisbee, fetch, and playing with other dogs should be preceded by a ‘warm-up’ period of walking.  In addition to regular controlled activity, rehabilitation activities such as stretching and range of motion exercises, controlled walking through or around obstacles, swimming, and under water treadmill work may be of benefit for many pets.

Aggressive medical management is frequently effective in the management of CrCLR in small breed dogs – about 80% of dogs under 30 pounds can be medically managed. In large breed dogs medical management has historically been thought to be overwhelmingly unsuccessful in returning dogs to full function.  A recent publication showed medical management success rates may exceed 50% in large breed dogs.  However, the successful patients lost at least 10% of their overall bodyweight during the study. Surgical management consistently outperforms medical management and offers the most predictable long-term outcome.  Please see our science based evidence page for more details.

Does My Dog Need Surgery?

The choice to pursue surgical management is typically based on patient size, the stage of disease, the amount of instability present, the expectations you have for your pet’s activity level and quality of life, and the presence of any other concurrent medical conditions (severe heart disease, uncontrolled hormonal disease, cancer, etc).  In some cases (patients with a very early partial tear of the cruciate ligament, obese patients, patients with minimal instability), medical management may be successful.  However, surgical treatment for rupture of the cranial cruciate ligament carries the most predictable outcome for dogs over approximately 30 pounds.

What ACL or CCL surgery is best?

Many surgical treatment options have been described for CrCLR.  Some of these originally focused on trying to recreate the CrCL within the joint, similar to how ACL ruptures are repaired in humans.  Unfortunately, the grafts that are used in dogs often break down similar to the original ligament and have not been found to have as high a success rate as some of the more current procedures.   Newer treatment options are divided into “extracapsular” and “osteotomy” techniques.

Extra-capsular techniques focus on using a synthetic material (varying types of suture or fishing line), which are placed at or around certain anatomic landmarks, in an effort to stabilize the joint and allow the formation of fibrous (scar) tissue. Some of these options include the traditional lateral extracapsular suture, the Tightrope, and the Swivelock.

The lateral extracapsular suture technique is the classical technique.  It utilizes a nylon line to provide stability.  Due to the low cost of the implant, the surgery is relatively inexpensive.  Unfortunately, this line can stretch and loosen through range of motion and though success rates for this procedure are reported around 85%, there is more and more evidence to suggest it is not the best procedure, especially in large breed dogs.  It is, however, a very successful and common technique used in dogs under approximately 30 pounds.

The Tightrope is a relatively new procedure that utilizes a strong synthetic suture as opposed to a nylon line. This material resists stretching, however, it is more prone to infection than nylon and in some surgeon’s opinions, outcomes are not as consistent as with the classic lateral suture technique. The Swivelock is a newer take on the Tightrope that utilizes a bone anchor in the femur instead of a bone tunnel.  This is also a new procedure that lacks significant research based results at this time.

Osteotomy techniques involve changing the biomechanics of the knee joint via osteotomy/cutting of the bone.  There are a large number of osteotomy procedures performed in veterinary medicine, but the overwhelming theme with all of them is achieving a reduction of the tibial plateau slope, or the tibial plateau angle (TPA).  The average TPA in a dog ranges from approximately 22°-25°.  The goal with most osteotomy techniques is to reduce this angle to approximately 5°-7°.

By changing the TPA, when a dog bears weight the forces acting on the joint are neutralized, and thus the tibia no longer thrusts forward in relationship to the femur.  In essence, these osteotomy procedures alter the biomechanics of the joint and eliminate the need for the CrCL.

Osteotomy techniques include the tibial plateau leveling osteotomy (TPLO), CORA based leveling osteotomy (CBLO), triple tibial osteotomy (TTO) and the closing wedge osteotomy.  Another osteotomy technique, the tibial tuberosity advancement (TTA) relies on the angle formed between the tibial plateau and the patellar ligament.  MVS primarily performs the TPLO in medium and large breed dogs (>30 pounds), as more and more evidence based literature shows improved outcomes with TPLO over other commonly performed procedures. See “Why TPLO”

The TPLO is one of the original osteotomy techniques and has been used in practice for over 20 years, with over a hundred research articles published on the topic.  This surgery involves the use of a semi-circular bone cut at the top of the tibia and rotating it to decrease the TPA.  The bone cut is then stabilized with a plate and screws.  Once the bone has healed, the plate and screws are no longer necessary, though they are typically left in place unless there is a problem associated with the plate such as infection or irritation.  Approximately 3-5% of patients who have the TPLO may, at some point in the future, need the plate removed.

What is the best surgery for my dog?

For dogs under 30 pounds, the lateral suture is a very effective technique for returning your pet to a high level of activity.  In medium and large breed dogs (>30 pounds), more and more evidence based literature shows improved outcomes with TPLO over other commonly performed procedures.

What are the risks of surgery?

As with any surgery, there are always potential complications when performing surgery. Anesthetic complications are possible, so it is important to consider a patient’s overall health prior to proceeding with surgery. Blood-work is recommended prior to surgery to ensure appropriate kidney and liver function and to help screen for other diseases processes. Minor complications such as swelling, bruising, or seroma formation are possible following surgery, and are typically self-limiting and resolve within a few days of surgery.

Implant failure is extremely rare, but is the most catastrophic potential complication.  Plates and screws used with the TPLO are very strong.  However, in rare cases when pets are allowed too much activity very early on in the healing process, it’s possible for the plate to bend or for the screws to bend or break.

Infection occurs in approximately 5% of lateral sutures and 7% of TPLO’s.  Some of these infections are limited to the skin, in which case a short course of antibiotics can successfully manage to problem.  In other cases, bacteria can get onto the implant and a patient must be maintained on antibiotics until the bone has completely healed (12-16 weeks after surgery), at which point the plate may need to be removed. Implant (plate) associated infections can occur weeks, months, or even years following surgery.  Approximately 3-5% of patients undergoing surgery will need to have the implant removed at some point in the future.

Meniscal injuries are possible with CrCLR.  The meniscus contains nerve fibers, and thus patients with a meniscal tear may exhibit greater pain and lameness than patients without a meniscal tear.  As previously mentioned, approximately 40% of patients with CrCLR will have a meniscal tear at the time of surgery.  The longer the cruciate injury has been present and the greater the instability in the joint, the more likely a patient is to develop a meniscal injury.  If the meniscus is torn at the time of surgery, the torn portion is removed.  If the meniscus is intact, in most cases it will be left without any treatment as it serves important roles for joint health.  There is evidence that dogs with meniscal injuries, and dogs in which a portion of the meniscus must be removed, have a faster progression of osteoarthritis.  Luckily, arthritis alone is rarely a cause of significant pain and lameness in dogs, as long as the underlying disease process (cranial cruciate ligament injury) is treated.  Approximately 10% of dogs that undergo surgery to repair a cruciate injury will at some point in time develop a meniscal tear.  However, it’s much more likely that a persistently unstable joint will go on to develop a meniscal tear than one that has been surgically stabilized.

Can this happen in the other leg?

Approximately 50% of all dogs who suffer a ruptured cranial cruciate ligament in one knee will go on to rupture the same ligament in the opposite limb – typically within 1-2 years of rupturing the first side.  Thankfully, the front legs in dogs are very similar to the human arm, so there are elbows, not knees, on the front limb.

What is recovery like for my dog?

The TPLO surgery involves making a bone cut (osteotomy), which is then stabilized with a bone plate and screws.  In essence, we create a fracture and stabilize the bone in a new position.  During this time we are completely relying on the implants to stabilize the surgery site. Despite the invasiveness of this procedure, dogs are generally comfortable very quickly following surgery (24-48 hours) and begin weight bearing on the surgical limb within days.  Though excessive activity can be destructive during the recovery period, frequent controlled weight bearing is invaluable to rapid bone healing.

The recovery period following a TPLO is approximately 8 weeks, as it takes approximately 8 weeks for bones to heal and good scar tissue to form.  The first 2 weeks of recovery are most critical to your pets outcome. It is extremely important that you restrict activity. There should be no running, jumping, playing with toys or other dogs. Your pet may go outside 3-5 times daily for 5 minutes at a time, on leash, for elimination purposes only.  After 2 weeks, if your pet is doing well, you may gradually start increasing the length of walks by 3-5 minutes/walk/week – in other words, week 3 your pet may go on ~10 minute walks on leash, week 4 ~13-15 minute walks, etc. By 8 weeks your pet can be up to two 20-30 minute walks per day, ALWAYS ON LEASH, with a couple shorter leash walks for elimination purposes.

You must prevent your pet from licking or chewing the incision site. Licking or chewing of the incision may cause premature removal of the sutures and/or incisional site infection, both of which may require a second procedure to repair. An E-collar must be in place at all times when your pet is not under your immediate supervision.

Passive range of motion exercises may benefit your pet by maintaining range of motion in the joint. We recommend 3-4 times a day, placing the surgical limb through complete range of motion, ensuring flexion and extension of all joints. We do not want to hurt your pet with this exercise, but ideally range of motion should improve day by day. We recommend flexing the limb to a point where your pet just begins to show discomfort, and then extending the limb in a similar fashion. This can be done for 15-20 repetitions each time.

Icing the limb for the first 3-4 days after surgery can help with pain control and inflammation. Please place a bag of ice or a bag of frozen peas, directly over the incision. Ice for 15 minutes per session. Placing a towel between the ice and the incision decreases the effectiveness of icing by not allowing the tissues to actually achieve a lower temperature, so this is not recommended.

After 3-4 days, you may begin heat packing the incision site. You may use a heat pack purchased from a pharmacy for this purpose, or you can fill a tube sock with rice and then heat it in the microwave. Remember, if it is too hot for your skin, its too hot for your pet. Heating can be performed for 15 minutes at a time, 3-4 times a day. This helps to reduce swelling and can also be performed prior to passive range of motion therapy.

If at any time during the recovery your pet stops using the operated leg, or fails to begin using the leg within 2 weeks, please contact MVS or your veterinarian.

Please follow your veterinarian’s instructions for administration of medications.

A bandage was applied to help reduce swelling and pain and to keep the incision covered. This bandage must be removed within 24 hours to prevent any bandage associated complications.  Your veterinarian can remove this bandage prior to discharge, or you may do it at home by slowly removing it layer by layer. Do not use scissors when removing the bandage at home, as this can lead to accidentally cutting the skin.

Your pet should be evaluated in 10-14 days to evaluate healing of the incision; sutures were placed in the skin and will need to be removed at this time. Please schedule this appointment with your veterinarian. If lameness occurs or your pet fails to improve, X-rays may need to be taken to verify proper implant position and evidence of healing. At 8 weeks post-surgery X-rays will need to be taken to verify complete bone healing before returning to normal activity. The implants are designed to stay in for life. However, if pain, infection, or irritation occurs we can easily remove these implants.

Will my dog ever run again?

With the TPLO procedure there is a reported 90-95% good to excellent outcome.  An excellent outcome is one where your pet can run, jump and play and you will not notice your pet has ever had a problem.  With a good outcome, after heavy activity your pet may have a short transient period of being sore and may need a short course of anti-inflammatories.  For one reason or another, 5-10% of patients will not return to a level of function that we expect.  It is important to note that just because your pet suffers a complication such as an infection or a meniscal injury, they can still have a good to excellent outcome – there just may be some hiccups along the way.

How much does surgery cost?

Board certified surgeons undergo 4-5 years of additional training beyond veterinary school,   with 3-4 of those years being specifically geared towards advanced surgical training. In addition, veterinary specialty care requires a large amount of specialized equipment.  The most well researched and consistently successful surgical repair for canine cranial cruciate ligament injury is the TPLO.  The TPLO surgery requires nearly a hundred thousand dollars worth of medical equipment including plates, screws, power drills and saws.

The average cost of a TPLO at a veterinary specialty referral hospital in Austin, Texas ranges from $3,000-$4,000.  The cost of a TPLO through an MVS participating practice is generally $500-$1000 less than at a specialty hospital.  Anesthesia, monitoring, implants, pre and postoperative radiographs, analgesia, hospitalization and go home medications are included.  Additional cost may be incurred at the 2 week recheck exam and at 8 weeks when radiographs of the knee are taken to confirm bone healing.

What in the world is a mobile surgeon?

Drs. David Allman and Kelly Might are board-certified small animal surgeons, Diplomates of the American College of Veterinary Surgeons.  Board certified surgeons undergo 4-5 years of additional training beyond veterinary school, with 3-4 of those years being specifically geared towards advanced surgical training.  As opposed to working at a stand-alone specialty hospital, Mobile Veterinary Specialists provides the service of coming to your family veterinarian’s hospital and performing the same specialty surgery in the convenience of your regular veterinarian’s hospital.  We bring all of our own equipment, while your regular veterinarian provides an operating suite, anesthesia, radiology services, and hospitalization.

Is there evidence that TPLO works?

Long-Term Functional Outcome of Tibial Plateau Leveling Osteotomy Versus Extracapsular Repair in a Heterogenous Population of Dogs

Samantha A. Nelson, MA, DVM; Ursula Krotscheck, DVM, Diplomate ACVS; Jeremy Rawlinson, PhD; Rory J. Todhunter, BVSc, PhD, Diplomate ACVS; Zhiwu Zhang, PhD; and Hussni Mohammed, PhD

• Dogs achieved normal limb loading faster after TPLO than extracapsular
• TPLO resulted in operated limb function that was indistinguishable from the control population by 1 year post-operatively.

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Comparison of lateral fabellar suture and tibial plateau leveling osteotomy techniques for treatment of dogs with cranial cruciate ligament disease

Wanda J. Gordon-Evans, DVM, PhD, DACVS; Dominique J. Griffon, DVM, PhD, DACVS; Carrie Bubb; Kim M. Knap; Meghan Sullivan, DVM, DACVS; Richard B. Evans, PhD

• Dogs in both groups improved after surgery
• Kinematic and owner satisfaction results indicated dogs that underwent TPLO had better outcomes than those that underwent lateral fabellar suture
• Owner satisfaction was 93% for patients undergoing TPLO

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Systematic Review of Surgical Treatments for Cranial Cruciate Ligament Disease in Dogs

Mary Sarah Bergh, MS, DVM, DACVS, DACVSMR; Carly Sullivan, BS; Christopher L. Ferrell, DVM; Jarrod Troy, BS; Steven C. Budsberg, MS, DVM, DACVS

• The strength of the evaluated evidence most strongly supports the ability of the TPLO in the ability to return dogs to normal function
• Provides strong support that functional recovery in the intermediate postoperative time period was superior following TPLO compared with lateral extracapsular suture.

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Complications with and owner assessment of the outcome of tibial plateau leveling osteotomy for treatment of cranial cruciate ligament rupture in dogs: 193 cases (1997-2001)

Nelson H. Priddy II, DVM, DACVS; James L. Tomlinson, DVM, MVSc, DACVS; John R. Dodam, DVM, PhD, DACVS; Jennifer E. Hornbostel

• Complications were identified in 20% of the TPLO’s
• 93% of owners were satisfied with the outcome of surgery
• Assessments of outcome were not significantly different between owners of dogs that had complications and owners of dogs that did not

Radiographic outcome and complications of tibial plateau leveling osteotomy stabilized with an anatomically contoured locking bone plate

Michael P.. Kowaleski, DVM, DACVS and DECVS; Randy J. Boudrieau, DVM, DACVS and DECVS; Brian S. Beale, DVM, DACVS; Alessandro Piras, DVM; Donald Hulse, DVM, DACVS, DECVS; Kenneth Johnson, MVSc, PhD, DACVS, DECVS

• Significantly fewer complications identified than previously reported with old surgical techniques
• No major post-operative complications