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Cranial Cruciate Disease in Dogs

First the Basics

Cranial Cruciate DiseaseThere are two cruciate ligaments which 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.

Finding the Rupture

Cranial Cruciate Disease

The ruptured cruciate ligament is the most common knee injury of the dog; in fact, chances are that any dog with a sudden rear leg lameness has a ruptured anterior cruciate ligament rather than something else. The history usually involves a rear leg suddenly so sore that the dog can hardly bear weight on it. If left alone, it 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 can be presented in either the acute stage (shortly after the injury) or in the chronic stage (weeks or months later).

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

Cranial Cruciate Disease

The veterinarian stabilizes 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” where the veterinarian stabilizes 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 side of the knee joint that faces the other leg. This is called a “medial buttress” and is a sign that arthritis is well along.

It is not unusual for animals to be tense or frightened at the vet’s office. 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 so a second opinion with an orthopedic specialist is a good idea if the initial examination is inconclusive.

Since arthritis can set in relatively quickly after a cruciate ligament rupture, radiographs to assess arthritis are helpful. Another reason for radiographs is that occasionally when the cruciate ligament tears, a piece of bone where the ligament attaches to the tibia breaks off as well. This will require repair and the surgeon will need to know about it before beginning surgery. Arthritis present prior to surgery limits the extent of the recovery after surgery though surgery is still needed to slow or even curtail further arthritis development.

How the Rupture Happens

There are several clinical pictures seen with ruptured cruciate ligaments. One is a young athletic dog playing roughly who takes a bad step and injures the knee while playing. This is usually a very 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 and chronic pain and loss of joint motion result. This process can be arrested by surgery but cannot be reversed.

  • Osteophytes are evident as soon as 1-3 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 under 30 lbs of body weight had regained near normal or improved function while only 19% of dogs over 30lbs had regained near normal function. Both groups of dogs required at least 4 months to show maximum improvement.

What happens in surgical repair?

Cranial Cruciate Disease
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.

There are 3 different surgical repair techniques commonly used, and a fourth method which has fallen out of favor in recent years:

Extracapsular Repair:

This procedure is currently favored as it can be performed in a relatively shorter surgery 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, outside on a leash only including the backyard)
  • The suture placed will break 2-12 months after surgery and the dog’s own healed tissue will “hold” the knee.

Tibial Plateau Leveling Osteotomy (TPLO):

Cranial Cruciate Disease
The TPLO rotates (as indicated by the arrow) the sloped tibial plateau until it is perpendicular to the line between the stifle and the hock joint centers.

This procedure uses a fresh approach to the biomechanics of the knee joint and is meant to address the lack of success seen with the above technique long term in larger dogs. With this surgery the tibia is cut and rotated in such a way that the natural weight-bearing of the dog actually stabilizes the knee joint. As before 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 in this specific technique. Many radiographs are necessary to calculate the angle of the osteotomy (the cut in the tibia). At this time the TPLO is felt by many experts to be the best way to repair a cruciate ligament rupture regardless of the size of the dog and is especially appropriate for dogs over 50lbs. This surgery typically costs twice as much as the extracapsular method and requires a specialist.

  • 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 are needed.
  • Full function is generally achieved 3 to 4 months after surgery and the dog may return to normal activity.


Tibial Tuberosity Advancement (TTA):

Cranial Cruciate Disease

The TTA represents another take on how to use the biomechanics of the knee to create stabilization. The idea is that when the cruciate ligament is torn, the tibial plateau (the top of the tibia) and the patellar ligament should be repositioned at 90 degrees to one another to combat the shear force generated as the dog walks. To make this happen, the tibial tuberosity (front of the tibia where the patellar 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 over 20,000 patients worldwide have have had this surgery. Some experts prefer it to the TPLO while others prefer the TPLO. Both procedures require specialized equipment and expertise.

  • Typically the leg is bandaged for a week after surgery.
  • The patients activity must be restricted and confinement is a must post-operatively with gradually increasing activity over 3-4 months. Most dogs can return to normal activity by 4 months after surgery.


Intracapsular Repair: (sometimes called the “over the top” method)

Cranial Cruciate Disease

We mention this procedure for its historical significance though it is not one of the “big three.” This procedure has fallen out of favor lately as it has been unable to demonstrate results superior to those of the extracapsular technique described above though apparently it is still a popular repair method in the U.K.

Intracapsular repair intuitively seems like it should do better as it uses living tissue (rather than an artificial material) to essentially make a new ligament. This takes more time surgically. As with the extracapsular repair, the knee joint is opened, fragments of the ligament are removed, as is damaged meniscus. After this a strip of connective tissue is dissected locally and passed through the middle of the joint exactly where the cruciate ligament used to be. The “new ligament” is attached at the opposite end to an implant or simply sewn into place.

  • Bandaging for a couple of weeks after surgery is commonly recommended.
  • Again, the dog may not bear weight for a good two weeks after surgery and will likely require 2 months to return to normal function.
  • Again, 8 weeks of exercise restriction will be necessary for healing.


General Rehabilitation after Surgery

Rehabilitation following the extracapsular repair method can begin as soon as the pet goes home. The area can be chilled with a padded ice pack for 10 minutes a couple times daily. (Do not try to make up for a skipped treatment by icing the area longer; prolonged cold exposure can cause injury.) Passive range of motion exercise where the knee is gently flexed and extended can also help. It is important not to induce pain when moving the limb. Let the patient 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. Rehabilitation for patients with intracapsular repair is similar but slower in progression.

Rehabilitation after TPLO or TTA is gentler. Icing as above and rest are the main modes of therapy. After 3 to 4 weeks, an increase in light activity can be introduced. A water treadmill is helpful. No jumping, running or stair-climbing is allowed at first. Expect the osteotomy site to require a good 6 weeks to heal.


What if the rupture isn’t discovered for years and joint disease is already advanced?

A dog with arthritis pain from an old cruciate rupture may still benefit from a TPLO surgery and possibly from the TTA. It may be worth having a surgery specialist take a look at the knee. Most cases must make do with medical management. Visit our section on arthritis treatment.

Meniscal Injury

Cranial Cruciate Disease
Looking head-on at this model of the flexed knee, one can see the menisci (cartilage pads separating the femur and tibia) as well as the cruciate ligaments crossing inside the joint.

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 and we would be remiss not to mention it.

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.

Areas of current research include techniques to improve blood supply to the healing meniscus so that repair can be more feasible. If meniscal damage has occurred in a cruciate rupture, arthritis is inevitable and surgery should be considered a palliative procedure.

Medial Luxating Patellas Dogs

Luxating patella – a knee cap problem in dogs

What causes the patella to luxate?

Cranial Cruciate DiseaseThe patella slides in a groove on the lower end of the femur (the bone that runs between the hip and the knee). There is a ligament called the “patella ligament” which runs from the bottom of the patella to the tibia, (the bone just below the knee joint). This ligament keeps the patella in place. The thigh muscles are attached to the top of the patella. When the thigh muscles contract, the force is passed through the patella and through the patella ligament, which results in straightening of the knee joint. The patella can luxate because the point where the patella ligament attaches to the tibia can sometimes be attached too far inward. As the thigh muscles contract, the force pulls the patella against the inner groove that it is sitting in.

After several months, the inner side of the groove wears down and the patella is free to move out of the groove or luxate. This can be quite painful when this happens and the dog may have difficulty putting weight on the leg. After a while, some dogs learn to kick the leg and push the patella back in place. However, because the groove is gone, the patella can easily move out of place again. Some dogs can tolerate this problem for a while, but the joint may become arthritic and painful.

Can a luxating patella be fixed?

A surgery called, “Medial Luxating Patella Repair”, can be performed.

There are three steps to the surgery:

  1. The point where the patella ligament is attached is moved and surgically fixed to its proper location.
  2. The groove where the patella sits is deepened so the patella will stay in place.
  3. The capsule around the knee joint is tightened.

It is important to have this surgery performed before arthritis occurs in the joint. If there is no arthritis, the dog should regain full use of its leg. If there is arthritis in the joint already, the joint can still be painful, especially in the cold weather.

View an automated slideshow of a luxating patella surgery below (coming soon).

Are there breeds that are predisposed to this condition?

The University of Sydney’s “Listing of Inherited Disorders in Animals” (LIDA) names the following breeds as being predisposed to this condition:-Cranial Cruciate Disease

  • Affenpinscher
  • American cocker spaniel
  • Australian silky terrier
  • Basset hound
  • Bichon frise
  • Border terrier
  • Boston terrier
  • Cavalier King Charles spaniel
  • Chihuahua
  • Dandie Dinmont terrier
  • English springer spaniel
  • Griffon Bruxellois
  • King Charles spaniel
  • Lhasa Apso
  • Maltese
  • Papillon
  • Pomeranian
  • Poodle (Miniature)
  • Poodle (Toy)
  • Pug
  • Shar Pei
  • Yorkshire terrier

How do you know if your pet has a luxating patella?

This condition is usually noticed in dogs less than two years of age. Signs range from mild to severe, and include temporary or occasional lameness possibly accompanied by a ‘hopping’ motion. Eventually the dog may hold the leg permanently off the ground. If both legs are affected, the dog may adopt a crouched gait and posture, appear bow legged and may even walk on the forelegs with the hind legs completely off the ground.

Prolapsed Third Eyelid Gland Dog Surgery

Canine Eyelid Diseases


Cranial Eyelid Disease

Entropion is a rolling-in of the eyelid. This causes the hair on the surface of the eyelid to rub on the eyeball, which is both painful and often causes corneal ulcers or erosions. The corneal damage can also result in corneal scarring, which can interfere with vision. Usually the dog will squint and tear excessively. However, many flat-faced dogs with medial entropion (involving the inside corner of the eyes) show no obvious signs of discomfort.

Entropion is treated by surgical correction (“blepharoplasty“), which is essentially plastic surgery. Excessive folds and sections of facial skin are removed, and the eyelids tightened. It is uncommon for entropion to recur after surgery unless the entropion is quite involved, particularly in the Shar Pei breed. Very young puppies with entropion will often have “lid tacking” performed (rather than plastic surgery), in which temporary lid sutures are placed to roll out the lids. Often, these puppies do not require permanent plastic surgery once they have matured and “grown into” their facial skin. Permanent plastic surgery is usually not performed in puppies less than 5 or 6 months of age, giving the dog some time to develop its mature head conformation.

Dogs with inherited entropion should not be bred, as they can pass the trait on to their offspring. The Canine Eye Registration Foundation (see CERF information) publishes a list of breed-specific breeding recommendations for purebred dogs with entropion.

If you suspect that entropion is present in your pet, please consult with your family veterinarian. Your doctor may elect to have your pet referred to a veterinary ophthalmologist for further evaluation and possible surgical treatment.


Cranial Eyelid Disease

Older dogs commonly develop eyelid tumors (cancer). As in humans, cancer can be either benign or malignant. Fortunately, eyelid tumors in dogs are usually benign and do not spread to distant tissues. However, eyelid tumors do slowly or quickly grow, and can destroy the structure of the eyelid, in addition to rubbing on the eye. It is usually best to remove them when they are still small.

Eyelid tumors are treated by surgical removal. While there are many different surgical procedures possible, most eyelid tumors in old dogs can be removed at Animal Eye Care without requiring general anesthesia. The patient is given a sedative, and then a local eyelid anesthetic is given to numb the eyelid. The tumor is removed and the site frozen with liquid nitrogen (cryosurgery) to kill any remaining tumor cells. Tumor cells are usually very sensitive to freezing, and normal eyelid tissue is more resistant. After surgery, the eyelid margin turns pink (depigments), but usually repigments within 4 months.

It is rare for the eyelid tumor to recur following surgery. 85-90% of tumors do not recur following surgery.


Cranial Eyelid Disease

Eyelids of dogs can grow abnormal hairs. These hairs grow from the oil glands (Meibomian glands) of the lids and are called distichia if the hair protrudes from the oil gland opening onto the edge of the eyelid. Distichia are often irritating, especially if the hairs are long and stiff. Ectopic cilia are also hairs growing from oil glands on the eyelid, but the hair protrudes from the inner surface of the eyelid and is very painful, often causing corneal ulcers.

Dogs with distichiasis may or may not show signs of discomfort, ranging from slight intermittent squinting and/or rubbing of the eyes, to severe squinting and discomfort. Dogs with ectopic cilia are always uncomfortable. Most dogs with ectopic cilia are young adult dogs or older puppies. Both conditions are common in Shih Tzus. Many other breeds have problems with distichia. At Animal Eye Care, both conditions are treated surgically under general anesthesia, with a procedure called cryoepilation. With this procedure, the abnormal hair follicles are frozen using a liquid nitrogen probe, and the hairs then removed.

After surgery, the eyelids are swollen for 4-5 days, and the eyelid margins will depigment and turn pink. Usually, the lid margins will repigment within 4 months. It is important to understand that new abnormal hairs can grow from new sites after surgery, but this is uncommon in dogs older than 3 years old (unless the dog is a Shih Tzu). With cryoepilation, 85-90% of the treated hair follicles will not regrow. Repeat surgical treatment is rarely required, unless the animal is a puppy (and grows new hairs in new sites) or a Shih Tzu.


Cranial Eyelid Disease

This condition is also called Prolapse of the Nictitans Gland. A slang term (which is to be discouraged) is “cherry eye”. Dogs have a third eyelid that slides up over the surface of the eye for protection. The third eyelid also has a tear gland located deep within its tissues, called the third eyelid gland TEG). Each eye of a dog actually has 2 tear glands (also called lacrimal glands), unlike people (who have one). The orbital lacrimal gland produces 60% of the tears for the eye, and the third eyelid gland produces 40% of the tears. The TEG has a T-shaped piece of cartilage in it, and is hidden out of sight and anchored to the tissues of the eye socket by ligaments. Some dogs are born with weak ligaments, which allow the TEG to pop out of its normal position and look like a pink roundish object in the inside corner of the eye.

PTEG is suspected to be inherited in some breeds, as it occurs with increased frequency in some breeds, notably the American Cocker Spaniel, Lhasa Apso, and English Bulldog. The condition can be in one eye or both eyes, and if in both eyes, it can occur weeks to months apart. Treatment is surgical, and involves repositioning the PTEG and suturing it into place. The prolapsed TEG should not be removed! If the condition is left untreated, the eye is at great risk for developing dry eye months to years later. Additionally the PTEG can swell and be uncomfortable, and interfere with vision. However, while surgery decreases the chances that the eye will develop a dry eye problem, it does not eliminate this risk.

The success rate of surgery is approximately 95% for non-recurrence of the PTEG, except in the English Bulldog and Mastiff breeds, in which the success rate is lower.

If you suspect that your pet has PTEG, please consult with your family veterinarian. Your doctor may recommend referral to a veterinary ophthalmologist for evaluation and surgical treatment.