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The knee is a fairly complicated joint. It consists of the femur above, the tibia below, the kneecap (patella) in front, and the bean-like fabellae behind. Chunks of cartilage called the medial and lateral menisci fit between the femur and tibia like cushions. An assortment of ligaments holds everything together, allowing the knee to bend the way it should and keep 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 (in animals called 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.
How Rupture Happens
Several clinical pictures are seen with ruptured cruciate ligaments. One is a young athletic dog playing roughly who takes a bad step and injures the knee. 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, Chesapeake Bay retriever, 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 or slowed 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 become permanently normal.
- In one study, a group of dogs was studied for 6 months after cruciate rupture. At the end of 6 months, 85% of dogs less than 30 pounds of body weight had regained near normal or improved function while only 19% of dogs over 30 pounds had regained near normal function. Both groups of dogs required at least 4 months to show maximum improvement.
What Happens in Surgical Repair?
There are three different surgical repair techniques commonly used, and a fourth method that has fallen out of favor in recent years.
This surgery is currently favored as it can be performed in a relatively shorter time than the other procedures and does not require specialized equipment. The knee joint is opened and inspected. The torn or partly torn cruciate ligament is removed. Any bone spurs of significant size are bitten away with an instrument called a rongeur. 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.
- 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).
- The suture placed will break 2 to 12 months after surgery and the dog's own healed tissue will hold the knee.
Source: By Wendy C. Brooks, DVM, DipABVP - VeterinaryPartner.com
Lateral orthopedic wire is shown taking the place of the anterior cruciate ligament. Usually thick suture is used rather than wire but for illustrative purposes the wire shows where the suture would be placed around the knee.
The medial luxating patella, commonly called a trick knee, is an extremely common problem in toy breed dogs. An owner typically notices a little skip in the dog’s step. The dog may even run on three legs, holding one hind leg up, and then miraculously be back on four legs as if nothing has happened.
In fact, something has happened: the kneecap (patella) has slipped out of the smooth groove in which it normally rides up and down. It has slipped medially, which is to say towards the opposite leg, as opposed to laterally, which would be away from the dog entirely. With the patella dislocated (or luxated) medially, the knee cannot extend properly and stays bent. Hopefully, the patient will be able to slip the kneecap back where it belongs and be back to normal in only a few steps. For some dogs, getting a kneecap back where it belongs and normal extension of the rear leg is a mere dream only attainable with surgical correction.
Approximately 50% of affected dogs have both knees involved while the other 50% has only one knee involved.
Which Dogs Need Correction?
Medial patellar luxations are graded to assess severity.
Grade I: The kneecap can be moved out of place manually but will fall back into its natural position once the manipulator lets go.
Grade 2: Same thing except that the kneecap does not move back to its normal position when the manipulator lets go. These dogs are likely to progress to arthritis development and should be considered for surgery to prevent conformational damage. There is some controversy over whether grade 2 dogs should have surgery.
Grade 3: The patella is out of place all the time but can be manipulated back into its normal position manually (though it will not stay there).
Grade 4: The patella is not only out of place all the time but cannot even be manipulated back into place by hand. Such a dog has extreme difficulty extending his knees and walks with his knees bent virtually all the time.
It is not a good thing to have one’s knee cap out of place; the entire weight-bearing stress of the rear leg is altered which, in time, leads to changes in the hips, long bones, and ultimately arthritis. How severe the changes are depends on how severe the luxation is (i.e., the grade as described above) and how long that degree of luxation has been going on. In time, the legs will actually turn outward with its muscles turning inward, making the dog bow-legged. The luxation is not considered a painful condition but after enough time and conformational change, arthritis sets in, which is indeed painful.
Dogs with Grade I luxations do not require surgical repair.
Grade 2 dogs may benefit from surgery and most often the owner is called upon to judge how big a problem the lameness is.
Dogs with Grade 3 or 4 disease definitely should have surgery.
This sugery is a procedure that not all veterinarians are comfortable performing. Discuss with your veterinarian whether referral to a specialist would be best for you and your pet.
What Surgical Procedures are Available?
Lateral Imbrication (also called Lateral Reinforcement)
This procedure alone may be adequate for a mild case but is often used as an adjunctive procedure to supplement one of the other surgeries. When the patella slips out of its groove, the joint capsule surrounding it is stretched to allow this motion. Imbrication simply involves taking a tuck in the joint capsule. The tightened joint capsule does not allow for the slipping of the kneecap and the kneecap is confined to its proper groove.
The patella rides in a groove at the bottom of the femur (thigh bone). In toy breed dogs this groove is shallow, which allows the patella to slip. If the groove is deepened, the patella stays where it belongs. The normal groove in the femur is lined by slippery lubricated cartilage, called hyaline cartilage. This cartilage is peeled or cut away, the bone underneath is sliced out to form a deeper groove, and the cartilage is replaced. Techniques that do not preserve the original cartilage are no longer recommended.
Tibial Crest Transposition
If the knock-kneed conformation has already started to set in, the tibias (or leg bones) will have rotated. In particular, the crest on the tibia where the thigh muscle (the quadriceps femoris) attaches may have migrated inward. If this is the case, the crest will have to be removed and pinned back where it belongs to straighten out the leg. Severe rotation of the tibias may involve actually cutting through the entire bone and de-rotating it back into place.
Should both Knees be Repaired at once or should they be Staged?
Some surgeons feel that doing one leg at a time, 8 weeks or more apart, is beneficial as the patient will have one good rear leg upon which to walk. If the patient is very young (under age one year) it may be a good idea to do both legs at the same time so as to prevent conformational problems in the leg not operated first.
If imbrication was the only procedure, expect 3 to 4 weeks of confinement. If any of the other procedures above were utilized, expect more like 6 to 8 weeks of confinement depending on the surgeon’s preference. During this time easy walking (no running or jumping) is helpful. The dog should be using the leg by two weeks post-operatively though some dogs must be retrained to use the leg after surgery. Physical therapy is in order if the dog is not using the leg after one month.
The American College of Veterinary Surgeons has included patellar luxation in their own web site medical library.
Source: By Wendy C. Brooks, DVM, DipABVP - VeterinaryPartner.com
If this article has caught your attention, it may be that your pet has had the misfortune of suffering a fractured bone. This is a traumatic experience for both you and your pet and there are a few things you should know to help both of you make the best of a bad situation!
First, it’s quite likely that your veterinarian will recommend surgical stabilization of the fracture. Indeed, dogs and cats with fractures are treated surgically more often than are humans.
There are two primary reasons for this:
Compared to humans, animals more commonly fracture the major bones closest to the body, the femur in the hind limb and the humerus in the front limb. (Fractures in these bones are often due to major traumas in our pets, such as automobile accidents.) Fractures of the femur and humerus do not lend themselves to stabilization with splints or casts.
Placing and maintaining casts or splints presents major challenges in dogs and cats. Keeping casts clean and dry, and avoiding pressure sores under the bandage material, can be nearly impossible in active pets. In addition, in very small animals, the weight of a cast or splint may make it difficult to impossible for the animal to move around.
If surgery is recommended, it will involve the application of various metal surgical implants such as pins, wires, plates, or screws. The primary goal of fracture fixation surgeries is to restore broken bones to their original anatomic position and rigidly fix them in place while healing occurs. In some cases, the fracture may be too severe to permit perfect anatomic restoration of all pieces, but there will still usually be a way of providing stability to the fractured bone and to allow use of the limb during the healing period.
After surgery, it will be your job as the owner to follow the post-operative care instructions very closely. While most animals will be encouraged to use the surgically-repaired limb, this activity must be under strict control. Surgical implants are strong but neither the implants nor the healing bone can withstand high energy or high impact movements.
Keeping the animal from licking at the surgical incision is imperative, at least until the sutures are removed. Persistent licking at a surgical wound will delay healing and is the major cause of incision infections.
How do you know if your pet is painful after surgery? Obviously, some discomfort is to be expected after the trauma of the injury and subsequent surgery. Your veterinarian will provide some pain relief, especially during the in-hospital period. After your pet comes home, you should watch for signs of pain by observing whether your pet is able to settle down, rest, and sleep. Animals in chronic pain have difficulty getting comfortable and will be reluctant to sleep for normal periods. You should also watch the limb for signs of swelling, redness, or discharge at the surgery site. The pet’s appetite and changes in the use of the limb are also critical signs to monitor. A patient who has been bearing some weight on the leg and suddenly stops doing so, or has a sudden decrease in appetite, should be reported to your veterinarian.
The following are a few common surgically-repaired fractures in small animals.
Humeral Condylar Fractures
Fractures involving the very end of the humerus, at the elbow joint, are common in puppies, especially between 4 to 6 months of age. These are most common in Spaniel breeds, but can occur in many other types of dogs. Most occur due to “impact injuries” (e.g., puppy jumped off a high place or fell from the owner’s arms). Surgery is necessary to reestablish normal function of the elbow.
Distal Radius and Ulna Fractures
Another “impact” fracture is commonly seen in small or Toy breeds of dogs. This involves fracture near the bottom of the front limb, just above the carpus or “wrist joint.” Pomeranians, Poodles, Chihuahuas, Italian Greyhounds, and Miniature Pinschers are some of the breeds that commonly get this fracture. It’s a particular problem in dogs with small, “spindly” bones because they have a more limited blood supply to this area of the bone than larger breeds do. The lower blood supply has a dramatic effect on healing of this fracture, so attempts at casting or splinting frequently meet with failure. Surgical stabilization, often with a bone plate and screws, brings much more consistent results.