Most dogs will appear to be Lame, or 'carrying' the leg after the rupture has occured. The injury may be a full rupture or a 'tear'. VETERINARY ADVICE must be sought.
This is very common in the Larger Breed and seems to be one of the most common complaints in ALL breeds, regardless of size. The following link may be of help.
Please note that permission must be sought from the Kennel Club to show after this operation.
Injuries to the cranial (or anterior) cruciate ligament are one of the most common orthopedic problems in dogs. In this pamphlet we will attempt to describe what is known about these injuries and their treatment. Despite decades of experience with this problem in dogs, there are still a number of controversies (especially in regard to treatment), and we will try to identify these unsettled areas in the text. Because there are such areas of debate it is possible that over time new information will be scientifically derived that may either settle these controversial areas, or add new consternation. Your best source for up-to-date information remains your veterinarian and a board-certified veterinary surgeon.
The canine knee (or “stifle”) joint is a hinge joint that is anatomically similar to the human knee. In fact, across many species and over eons of time the basic anatomic structure has remained fairly constant, with evolutionary modifications that are species-specific. Injuries to the anterior cruciate ligament are very common in people too (so-called “football knee”), and this has led to useful, but in some cases potentially erroneous comparisons between human and dog knee problems.
The cruciate ligaments reside deep within the knee joint and cross (hence their name) each other as they attach the two major bones of the knee, the femur (thigh bone) and tibia (shin bone). The cranial (anterior) ligament is much more commonly injured than the caudal (posterior) ligament. There are other stabilizing ligaments in the knee as well, but these are rarely injured except with catastrophic trauma (and such severe injuries often result in tearing of both cruciate ligaments and at least one of the collateral ligaments that reside on either side of the joint, along with other structures). Such catastrophic trauma that results in tearing of three or more ligaments and other injuries is termed “deranged knee”, and is not the situation facing most people or dogs with cruciate ligament problems. For the purposes of this pamphlet, “cruciate ligament” will refer to the cranial (anterior) ligament only, unless otherwise specified.
Because the bottom part of the femur (called the “condyles) does not fit congruently with the top part of the tibia (called the “plateau”), small cartilage spacers have evolved to improve the articulation of the two bones. These cartilaginous spacers are known as the menisci (meniscus = singular). The medial (inner) meniscus is more frequently injured than the lateral (outer) meniscus, and this “torn cartilage” injury is frequently encountered as part of the cruciate ligament problem.
SEE FIG 1 (drawings of knee anatomy with labeled structures)
WHAT CAUSES CRUCIATE LIGAMENT PROBLEMS?
In humans the anterior cruciate ligament (ACL) is usually torn as a result of a sports-related injury. Such injuries typically involve either hyperextension of the knee, forcible internal rotation of the lower leg, or combination of these. It is generally an acute injury that the person is immediately aware of.
For many years it was assumed that the mechanism of dog knee injuries mimicked what was seen in humans. Probably, some dogs truly injure their knees this way, for example a running dog that steps into a hole and hyperextends the knee as it continues forward. However, many of the knee injuries in dogs seem to occur without any such violent trauma, and this suggests that there may be some other factor(s) at play.
The main functions of the cranial/anterior cruciate ligament are to prevent forward sliding of the tibia relative to the femur, excessive internal rotation of the lower leg, and over-extension (straightening) of the joint. It is not surprising then that forcefully exceeding the limits of the cruciate ligament to withstand such motions results in ligament rupture. But while the situation is readily understood in humans, we still have the conundrum of dogs that tear their ligaments without such forceful exceeding of ligament strength. How can this be explained?
“Anatomy is not the whole answer”
We already alluded to the similarities between the canine and human knee. It is not surprising therefore that this would have led to assumptions that injuries occur similarly. In turn, this led for many years to assumptions that treatment for canine cruciate ligament injuries should be the same as those used for people. But this may not be the case. In fact, we have recognized not only the absence of specific histories of trauma with our canine patients (“gee, all we do is go for walks and the dog just started limping for no reason”), but other things that seemingly did not “fit” with the concept of canine and human knee problems being exactly comparable. These include:
The recognition of these and other anomalies caused veterinarians and veterinary surgeons to look for other factors that might be involved. Over the years many theories have been proposed, but none of these seem to stand up to either logic or scientific scrutiny. For example, it has been known that dogs with cruciate ligament injuries frequently are found to have a specific type of inflammation in their knee joints when the joint lining is biopsied. This led to speculation that affected dogs might have some underlying rheumatological disorder that caused the cranial cruciate ligament to weaken and degenerate. However, there are major flaws with this theory. First, it was never established whether the inflammation seen came before or after the ligament injury occurred. Even more damning, the two cruciate ligaments (cranial/anterior and caudal/posterior) lie within exactly the same space and milieu within the joint. How could an inflammatory/degenerative process affect one ligament but not the other?
The breakthrough to our modern understanding is a classic in looking at an old problem with new eyes. Although we recognize that the anatomy of canine and human knees is similar, the posture and biomechanics of the knee are markedly different between man and dogs. Humans stand with their heel bones flat in the ground, and their knees are almost straight when weight bearing. Dogs, however, stand on their toes, with their heel bones (“hock”) up in the air. Their knees are bent at an angle. By virtue of this postural difference it can be shown that dogs develop extra vectors of force in their knees when they are bearing weight. This is generally a shearing force that tries to push the tibia forward relative to the femur. This shearing force is termed cranial tibial thrust. It is believed that dogs with normal knees counterbalance these shearing forces via the large muscles on the front of the leg (quadriceps or “quads”) and the large group of muscles behind the knee known collectively as the “hamstrings”. The current theory is that some dogs (and this may be the heritable, breed-related factor alluded to above) have shearing forces that exceed the ability of their muscles to restrain them. As a result, the force is transferred to the last link in the chain – Mother Nature’s “emergency brake” if you will – the cranial cruciate ligament. If this theory is correct, it implies that most of the cranial cruciate ligament injuries we see in dogs are not the result of any single, acute trauma, but the effects of thousands of smaller traumas accumulated over time. These types of injuries are described as repetitive stress injuries. The theory holds that predisposed dogs are giving a microscopic “jerk” to their ligament every time they take a step or bear weight while running, jumping, etc. Over time the ability of the body to repair these small injuries is outpaced by the addition of new injuries, starting the process of ligament degeneration. As this process goes on we start to see the recognizable partial and complete tears of the cruciate ligament. Moreover, once the ligament becomes significantly weakened, it is even less able to restrain forward shearing motion, and the process accelerates. The acute lameness seen in many dogs may really be the end-stage of a long process of degeneration, rather than a truly acute injury.
This new paradigm helps explain some of the observations and apparent discrepancies listed above, and also suggests alternative methods for treating cruciate ligament injuries in dogs.
The foremost thing to say here is that there is no controversy that surgery is the best option for managing dogs with cruciate ligament injuries. Many studies and experience have shown that the long-term prognosis for good function, pain control, limitation of arthritis, and so forth is better in dogs that have had there knees operated on than those where conservative therapy alone has been used. The controversial aspect is what type of surgery is best?
Conventional Surgical Reconstruction
Long before there was any understanding of the active force model described above, the assumption for both people and dogs was that “If the rope is broken you need to repair or replace the rope”. For decades the focus was on new and improved ways to rebuild the rope, or otherwise reproduce the stability that had been provided by the cruciate ligament. Over the years many new and innovative ideas were developed, and then each of these underwent some individualized modifications. This has resulted in there being literally dozens of techniques for cruciate ligament reconstruction, varying in such things as what material is used to create the new “rope” and how it is placed and anchored in the joint. Regardless of the specific nuances of any one technique, they all share the common goal of eliminating passive instability; success being measured as the elimination of the drawer sign. In many studies looking at results with various techniques they all perform about equally. So while one surgeon may prefer one method of repair, and someone else does things differently, both can be expected to have similar results so long as they are familiar with the specific operation they have chosen to do.
This type of operation works well for humans, and generally is also very effective for smaller dogs. However, the results have been less predictably good for larger and more active dogs. As said at the outset, it is still far better than no surgery at all, but the frustration in veterinary medicine is that regardless of modifications and improvements in technique, most studies show that only about 80-85% of dogs will have good to excellent function after such surgery. The other 15-20% persist in having some degree of lameness or other complications. Not only do we have too many dogs with ongoing disability (hopefully just mild, but sometimes more profound), we cannot predict which knees will do better and which will do less well. This occurs despite performing virtually identical operations in knees with essentially identical pathology. Moreover, how we define “good to excellent” may not be stringent enough. Our goal in surgery is always to strive for perfection. We may never achieve 100% success in our results, but by aiming for a higher percentage of successful outcomes, and by critically assessing what we call “good” or “excellent” we try to have more and more animals restored to near normal function after cruciate ligament injury than we have previously attained.
Active Force Reduction Surgery
Given the foregoing understanding of how canine cruciate ligaments are injured, and the limitations we have encountered with our best efforts at conventional, “replace the rope” type surgeries, veterinary surgeons have embarked on newer methods for treating these injuries. The concept is this: If the problem isn’t so much the absence of the cruciate ligament, but the shearing force (tibial thrust) that caused the ligament to fail in the first place, shouldn’t our attention be focused on eliminating the latter? After all, if there is no tibial thrust/shearing force, one theoretically would not even need a cruciate ligament (or a substitute for a torn ligament) since you have then eliminated the biomechanical factor that the cruciate ligament was there for.
A review of basic physics and trigonometry (which we will not undertake here) demonstrates that force vectors can be changed by alterations of geometric angles. This forms the basis for the newer cruciate ligament surgical procedures in veterinary medicine. By eliminating the shearing force the knee becomes stable during weight bearing. If the cruciate ligament “rope” is not replaced the dog will still have passive instability (drawer sign), but this is not clinically significant since we are only concerned with how the knee functions when the dog is walking and running on it, and not just a test done with the dog on its side. The only concern about not specifically treating the passive instability is that this may leave the dog prone to secondary meniscal cartilage injury. This is addressed further below.
When normal canine anatomy is reviewed it is apparent that there is a backwards, downsloping angle to the upper part of the tibia, the tibial plateau, and the long axis of the bone. When the cruciate ligament is torn this tibial slope allows the femoral condyles to move backwards and downwards along the tibial plateau as the tibia moves forward from cranial tibial thrust. Imagine a wagon on an inclined plane or hill, where the front of the wagon (femur) is tied to the front of the inclined plane (tibia) by a rope (cruciate ligament). With the rope cut the wagon rolls down the hill. Conventional surgery, as we have seen above, works to try and restore the rope. However, because of tibial thrust, the new rope tends to weaken and stretch. This results in several things: First, the knee may develop recurrent passive drawer since the new rope is no longer tight. This is exactly the situation we have long recognized happening after conventional repairs; Second, the active instability persists, causing ongoing lameness or limitation in normal function, another recognized clinical problem in some knees after conventional repair; Third, the meniscus (see above) is “rolled over” by the femoral condyle as it moves down the tibial slope. This is recognized both as the torn meniscus (torn cartilage) very commonly found as part of the original injury process in dogs with cruciate ligament injuries, and also by the finding of some dogs developing a torn meniscus weeks to months after conventional surgical repair.
The newer operations try to eliminate this active instability by changing the anatomic relationships so as to reduce the shearing force vector to zero. Rather than replacing the rope, these operations make the rope moot by eliminating the inclined plane and forward shearing thrust.
The most common and best studied operation to make this geometric alteration of the knee is the tibial plateau leveling osteotomy (TPLO). Other operations with similar goals (and slightly different trigonometric underpinnings) include the tibial tuberosity advancement (TTA), and tibial wedge osteotomy (TWO). Newer techniques and refinements of more established techniques continue to be introduced.
Surgery is done under general anesthesia which is typically complemented with an epidural anesthetic and analgesic (pain) medication placed directly into the joint. The strictest standards for sterility are utilized to reduce the risk for infection. This requires extensive shaving of hair and other preparations. Usually two or more surgeons are present for TPLO surgery. If radiographs had not been taken previously they are taken, and measurements made, immediately before preparation for surgery.
The surgeon first explores the knee to evaluate damage to structures such as the menisci. This can be done arthroscopically (“scoping”), or can be done by actually incising into the joint (arthrotomy). If the meniscus (typically the medial one) is torn the surgeon will remove the torn portion. With or without a tear, the surgeon may also perform a meniscal release. As mentioned above, the recurrence or persistence of passive drawer (expected with TPLO and common, with time, after conventional repair) potentially allows the femoral condyle to roll over, crush, and tear the meniscus. Meniscal release is intended to make the meniscus less vulnerable to such a post-operative injury. It is one of the areas of controversy however, and is still under study to determine both how helpful it is, as well as any problems doing this procedure might actually cause.
The actual TPLO involves making a curved cut through the upper part of the tibia with a special power saw. This frees the tibial plateau and allows its rotation to a lower angle relative to the long axis of the bone. Where the cut is made, and the amount of rotation applied, are based on preoperative x-ray measurements and other factors determined by the surgeon. In some dogs the preoperative exam and radiographs will actually demonstrate some abnormal inward or outward twisting (called tibial torsion), and this might be corrected as part of the TPLO procedure. After the bone is rotated it is stabilized in the new position with a metal bone plate and multiple screws. The plate must be molded by the surgeon to the exact shape of the dog’s bone during the operation. (FIG) Once the osteotomy is stabilized the incisions are closed with multiple layers of sutures, with a final layer of sutures or surgical staples in the skin. Post-operative x-rays are taken to assess the new tibial slope and the position of the bone plate and screws. A compression bandage may then be applied for the first 24-36 hours.
TIBIAL TUBEROSITY ADVANCEMENT (TTA)
This is a newer operation for modifying the geometry of the knee to eliminate shear forces. It appears to be comparable to TPLO, and studies are underway to determine if one produces better results than the other. Currently the choice between TPLO and TTA is largely a matter of surgeon’s preference and some other, subtler factors.
TTA involves making a linear or slightly curved osteotomy (cut in the bone) between the tibial tuberosity in the front and the main portion of the shaft behind. Guided by pre-operative x-ray measurements, the tibial tuberosity is shifted forward (advanced) so as to achieve a perpendicular relationship between the straight patellar tendon (the tendon that links the kneecap to the tibia) and the tibial plateau (see under TPLO above). The advanced tibia is held in this position with two devices: One is a titanium “cage” or spacer that is wedged between the tibial tuberosity and the shaft, and the other is a titanium plate that affixes the bones in the new position. All the implants are secured with screws and pegs anchored into the underlying bone, and finally a bone graft (usually harvested at the surgical site from the patient’s own leg, but sometimes augmented with “banked” bone graft) is placed between the bones to promote faster healing. Wound closure and post-op care are essentially identical to that for TPLO.
TRIPLE TIBIAL OSTEOTOMY (TTO)
You will play a critical role in the outcome of your dog’s surgery. There are some basic steps that you can follow that will help insure a positive end result.
Before, during and after surgery several different pain management techniques were utilized to help keep your dog comfortable. Once your dog goes home you will be engaged in continued pain management.
You will need to give prescribed medications that control pain and reduce swelling in the knee joint. The medications used will in part be dependant upon what medications he/she had been taking prior to surgery. Almost all dogs will be discharged from the hospital with a fentanyl patch on their skin. Fentanyl is a narcotic that helps control pain. The patch will remain on your pet for 3 to 5 days. Your doctor will tell you when the patch should be removed.
There are several different non-steroidal anti-inflammatories currently available that could be prescribed for your pet. Your doctor will select the drug he/she feels is most appropriate for your dog. Specific instructions as to dose and dosing schedule will be provided. The most common side effects of these medications include nausea, inappetance, melena (dark, tarry stools) and possibly vomiting. If you notice any of these symptoms in your dog, stop giving the medication and contact your doctor.
Just like us, dogs benefit from rehabilitation therapy after surgery. Rehabilitation therapy has multiple goals. The first is to help improve your dog’s comfort. If your dog is more comfortable he/she will be more willing to use his/her leg and permit other rehabilitation therapy exercises. The second goal of rehabilitation therapy is to help restore your pet’s knee and overall function faster and more completely by preventing loss of muscle mass and improving range of motion. Muscle is lost when a limb is not being used. It has been shown that muscle cells will start to atrophy (shrink) within 24 hours of surgery. Aggressive rehabilitation therapy in the first few weeks can minimize this atrophy and accelerate recovery.
Rehabilitation therapy will start before your dog even wakes up from surgery and will continue while he/she is hospitalized. Once home, you will take over this vital role. You’ll start by applying a cold compress (ice pack) to the knee for 10-15 minutes three times daily. This will help reduce swelling and inflammation, which will significantly improve comfort.
Passive range of motion (PROM) will start shortly after your dog goes home. These exercises are designed to get your dog’s operated joint(s) moving, which will help improve comfort and encourage limb use. You will be instructed in proper technique for exercises your pet will need.
Stretching is also important. If your pet has been lame for several days, or even longer, the muscles of his/her limb and back will be stiff and sore. The stretching exercises will help make these muscles more supple, which will help improve overall comfort and encourage limb use. You will be instructed in proper technique for exercises your pet will need.
Stretching and PROM exercises will need to be performed at least once a day during your dog’s recovery. It will take about 15-20 minutes to perform these exercises once both you and your dog get used to them.
Many dogs will benefit from starting these exercises before surgery. Starting rehabilitation before surgery (“prehab”) allows both you and your dog to become familiar with the exercises needed before his/her knee is uncomfortable because of the surgery performed. “Prehab” can also help regain some lost muscle mass and improve muscle comfort before the onset of surgical discomfort, which will accelerate your dog’s recovery process. A specific rehabilitation program can be designed for your pet by our rehabilitation staff. They will be able to apply more advanced rehab techniques to further facilitate your dog’s recovery. We strongly encourage you to enlist the rehab staff in assisting your dog’s rehabilitation process. You may contact the staff of the Animal Rehabilitation Center of Rochester at 585-663-4262.
The most difficult aspect of your dog’s recovery will be enforcing the exercise restrictions needed to allow your dog to heal with minimal complications. At times it will be hard to say ‘no’ when he/she is asking you to go out and play because they are feeling better. It is important to remember that your dog is feeling better because he/she has had major orthopedic surgery, and that it will take several weeks to months for adequate healing to occur to permit activity. Too much activity can compromise the surgical repair. In the best case, too much activity will simply make your dog more painful. In the worst case the surgical implants will be overstressed and fail, potentially necessitating additional surgery to correct the problem.
Immediately after surgery your dog will need to be confined to a crate or small space with non-slip flooring. The size of space permissible will be dependant upon the size of your dog. Your doctor will tell you what is acceptable.
Your dog will be able to go outside for short (5-10 minute) leash walks for bathroom breaks. Whenever your dog is out of this confined area he/she should be on a leash and have a sling slipped under the belly, just in front of the rear legs. You will be provided with a sling when your dog is discharged from the hospital. The sling is not meant for you to lift your dog, it is there simply as a safety net if he/she slips or stumbles. Exercise limitations will be re-evaluated and adjusted at each post-operative recheck.
You will also need to monitor the incision for problems. Check the incision daily for signs of infection, which include heat, swelling, pain, discharge and redness. If you see any of these problems please contact your doctor. One of the more common sources of infection is your dog’s mouth. The physical trauma caused by licking and chewing, combined with the moisture deposited at the incision from your dog’s mouth creates an environment ideal for bacterial growth. Your dog will be sent home with a plastic collar (Elizabethan or “E” collar) that will help prevent your dog from traumatizing the incision. Leave the E-collar on at all times. Most dogs can eat and drink with the E-collar. If your pet is having difficulty negotiating the food and water bowls with the E-collar on try raising the bowls off the floor. This will eliminate any difficulty your dog was previously experiencing.
The staples/sutures in the incision will need to be removed approximately 10 days after surgery. You can schedule this appointment at the time your dog is discharged from the hospital.
The first major recheck occurs about 6-8 weeks after surgery (TPLO and TTA). Radiographs (xrays) of the knee are taken under general anesthesia to evaluate the healing of the bone and to check the implants for potential problems. Your dog’s knee will not be completely healed at this time after surgery. If sufficient healing has occurred your dog will be allowed to have a bit more activity at home. This will include slightly longer leash walks and, possibly, some supervised freedom in the house. Your doctor will provide details of the exercise permitted based on the appearance of your dog’s knee during the recheck. If you are utilizing the services of the Animal Rehabilitation Center advanced rehab therapy will be initiated under the supervision of your doctor.
A second, and probably final, appointment may be scheduled 6 weeks after the first recheck (12 weeks after surgery). Radiographs will be repeated under general anesthesia. The surgery site will have healed at this point in most patients.
Once healing has been confirmed your dog will be able to be re-introduced to his/her normal activities. It will be important to remember that although the surgery site has healed neither it nor your dog are as strong at they were before surgery. Your dog has been on ‘bed rest’ for several weeks so cardiovascular fitness will be compromised. Please remember to take things slowly. Gradually increase the length of walks your dog takes. Every week add another 10-15% to the length of the walks taken. Each time you increase the length of the walk, expect your dog to be a bit uncomfortable.
Continue to provide supervision when your dog is not confined to a crate or small space. When your dog is back to his/her normal leash walking routine you can start to allow short (3-5 minute) periods of supervised activity off leash (in a controlled environment). Gradually extend these periods using the same principles applied to extending the length of walks taken. In most patients, complete return to normal activities takes place approximately 2 months after the last radiographic recheck.
More than 90% of the dogs that have TPLO or TTA surgery regain normal or near normal function of the limb (full weight-bearing). We have operated many dogs that have resumed normal working activities (police dogs, hunting, agility). Dogs that have sustained a blowout fracture of the tibial plateau as a result of falling after surgery will not regain as good of function on the limb. Dogs that have been previously operated using another technique frequently are improved with the TPLO or TTA surgery, but the outcome may not be as good, versus a virgin knee that has received the TPLO or TTA surgery. The TPLO or TTA procedures will help to minimize the progression of degenerative joint disease. One study demonstrated a four fold reduction in the progression of arthritis following TPLO surgery, versus dogs that received the lateral imbrication technique.
Infection: unusual complication as strict sterile technique is used during the surgery.
Poor bone healing: this can occur if your dog is overactive or if your dog is receiving medications such as chemotherapy or steroids.
Patellar ligament strain: following TPLO surgery the patellar ligament will have a significantly increased pressure exerted on it and may become strained if your pet is overactive during the healing phase. Rest and anti-inflammatory medication are used to resolve this problem.
Tibial crest fracture: as mentioned above the patellar ligament will have significant increased force exerted on it and the bone that it is attached to will also have more force applied to it. The result can be a fracture of the tibial crest. This will typically heal without additional surgery.
Implant failure: the screws may loosen, bend or break if your pet's activity is not restricted or if he/she takes a fall. This may also result in a catastrophic fracture of the top part of the tibia.
Arthritis: this is typically present in most dogs that have a cranial cruciate ligament rupture. The arthritis could progress with time and result in stiffness of the limb. Medications are used to help relieve these clinical signs.
Anesthetic reactions are uncommon and rarely result in mortality under the care of our trained specialists and nurses.
Meniscal tear: this is a complication that occurs in about 2% of dogs following TPLO Surgery and 30% of dogs following traditional repairs. This would necessitate another operation.