Luxating Patella

OVERVIEW: 

 

Patellar Luxation is one of the most common skeletal problems found in small dog breeds and among the most common serious conditions in general.  Patellar Luxation is also sometimes referred to medically as luxating patella or luxating patellas, depending on whether one or both knees are affected.  There are also a wide range of colloquial terms for the condition, among the most common of which are loose knee, slipped knee, slipping knee, and trick knee.  Because the patella is located in the hind leg of the dog, only the hind legs are impacted by this condition.

 

Patellar Luxation occurs when a dog’s kneecap shifts to an improper location within the leg.  The natural position of the knee cap, or patella, is inside of a special groove on the dog’s femur, or leg bone.  As the dog walks, the patella moves up and down the groove in a set path.  The patellas of dogs suffering from luxating patella move outside of that groove.  There are many forms and variations of patellar Luxation.  For example, the condition may either be unilateral, meaning that only one leg is affected, or bilateral, meaning both legs are affected.  The condition may also either be an isolated single event or a chronic recurring condition.  Patellar Luxation also widely varies in its severity.  Some cases are so mild that they only last for a few minutes and are unnoticeable to observers while others are so severe that they cause permanent, crippling damage.

 

The impact on the dog caused by patellar Luxation varies widely depending on the severity of the condition.  In minor cases, the dog may not seem to be impacted at all, or at most suffer from a few moments of pain or reduced movement.  In severe cases, the dog may be in so much pain and discomfort that it is completely unable to walk.  Most cases are somewhere in between these two extremes, leaving the dog in pain and discomfort and with substantially reduced mobility.

 

In order to help them classify and treat the many variations of patellar Luxation, veterinarians have devised a grading scale for the severity of patellar Luxation which includes four categories.  Grade I patellar Luxation is the mildest form.  The patellas of impacted dogs usually quickly return to their natural positions, often without manual maneuvering.  Grade II is defined by patellas that are usually in their natural positions, but may come off track occasionally.  The patellas of dogs suffering from Grade II patellar Luxation may require manual maneuvering to return to their proper placement but often do not provided the dog extends the joint and de-rotates the tibia.  Grade III is defined by patellas that are luxated most of the time and require manual maneuvering to return to their proper track.  Grade IV is the most severe form of patellar Luxation.  The patellas of dogs suffering from Grade IV patellar Luxation are permanently off-track and cannot be manually maneuvered back into place.

 

The causes of patellar Luxation are not completely understood.  One known cause is trauma, such as an accident or injury.  Although still fairly common, trauma-caused patellar Luxation cases are a small minority of the total number.  Most cases are a result of genetics.  The exact genes responsible are not known, and most researchers now believe that patellar Luxation is a polygenic condition, meaning that several different and possibly unrelated, genes are responsible.  Many researchers believe that a malformed femur, patella, tibia, or groove is responsible for patellar Luxation in many cases, although it does not appear that this is a universal consensus.  Other veterinarians have suggested that malformation of tendons and ligaments may also play a key role.  Although it is widely agreed that patellar Luxation is hereditary in nature, there is no agreement on exactly how it is inherited.

 

Although patellar Luxation is not life-threatening, it can be a very serious condition.  An isolated incident will cause a dog great discomfort and reduced mobility until it is successfully treated.  Dogs are likely to limp or refuse to put weight on a leg with a luxated patella, or may not be willing or able to move at all if both patellas are luxated.  Chronic problems, even if each individual occurrence is very mild, can have long-lasting and permanent effects.  Repeated occurrences can further damage the patella and/or other leg bones, resulting in a number of complications.  Most frequently, osteoarthritis results from long-term untreated patellar Luxation, a condition that can be every bit as painful and crippling as patellar Luxation itself.

 

RISK FACTORS: 

 

The following factors have either been shown to or are widely believed to increase a dog’s chances of developing patellar Luxation:

 

  • Breed: Certain dog breeds are known to suffer from high rates of patellar Luxation.  Some of the breeds most likely to exhibit patellar Luxation include: Miniature Poodles, Toy Poodles, Chihuahuas, Labrador Retrievers, Boston Terriers, Yorkshire Terriers, Basset Hounds, Pekingese, Shih Tzus, Lhasa Apsos, and a number of other breeds.
  • Size: Patellar Luxation is one of the few conditions which are considerably more prevalent in small dogs than larger dogs.  Although there are many exceptions, generally the smaller the dog the more likely it is to develop patellar Luxation.  Although highly disputed by their breeders, most in the veterinary community believe that extremely small dogs, usually those described as Tea Cup, Tiny Toy, or related terms, are considerably more likely to develop patellar Luxation than normally sized breed members.
  • Other Conditions:  Although more studies need to be conducted for more information, most believe that dogs with other skeletal problems are more likely to develop patellar Luxation.  This is especially true of those conditions which impact a dog’s leg structure or its walking such as hip and elbow dysplasia, panosteitis, and skeletal growth abnormalities.  The presence of other skeletal problems and abnormalities can also impact the severity of patellar Luxation and the likelihood of surgical success.
     

 

SIGNS & SYMPTOMS: 

 

The signs of symptoms of patellar Luxation vary greatly depending on the severity of the condition.  Dogs with very mild cases may not show any symptoms until after they have had the condition for some time.  The owner usually notices something wrong when their dog seems to have reduced mobility or discomfort when walking, symptoms that gradually increase over time.  The actual patellar Luxation may not be visible to the naked eye in such cases, or it may return to normal so quickly that an owner is not able to see it before the problem is solved.  Dogs with more severe cases have much more obvious symptoms.  One of the most common is limping or reluctance to put weight on one or both legs.  This limping can develop very quickly, sometimes nearly immediately.

 

Dogs with patellar Luxation in both legs may refuse to move entirely.  In some cases, a dog may refuse to move an affected leg entirely, even holding it out from the body.  Some dogs repeatedly shake their legs in an attempt to return the patella to its normal position.  Most dogs suffering from severe cases of patellar Luxation show signs that they are clearly in pain such as whimpering, heavy breathing, and/or refusing to participate in activities that they usually enjoy.  Sometimes, the patella is so far off track that even a veterinary novice can clearly see the problem.  The longer that patellar Luxation goes untreated, the more severe the symptoms usually become.  In cases of chronic severe patellar Luxation, a dog may also exhibit weight gain or more rarely loss as a result of decreased activity.  Puppies experiencing patellar Luxation often appear to be bow-legged.  If the condition is not corrected, the dog becomes increasingly bow-legged as it ages.

 

DIAGNOSIS & TESTS: 

 

Patellar Luxation is very simple for a veterinarian to diagnose.  A veterinarian will review a dog’s symptoms and manually examine the dog’s hind legs.  In particular, the dog’s patellas will be manually maneuvered and examined.  A quick manual exam is often enough to determine the grade (severity) of the patellar Luxation, and also whether or not the condition is unilateral or bilateral.  Most veterinarians will follow up a manual examination with x-rays.  X-rays can help to more accurately assess the grade of the patellar Luxation, and also to identify it in cases where the symptoms are so mild that the veterinarian may have trouble identifying them visually or manually.  Perhaps most importantly, x-rays will allow the veterinarian to determine if the condition has caused serious side effects such as osteoarthritis.  If the veterinarian deems it necessary, 3-D medical imaging technology may also be employed to give the fullest picture of the extent of the condition.

 

CONVENTIONAL TREATMENT & MANAGEMENT: 

 

The treatment necessary to correct patellar Luxation varies depending on the severity of the condition.  Very mild cases often correct themselves without any intervention and may not require any veterinary treatment.  This is especially true of mild, single cases.  Dogs experiencing pain or discomfort as a result of long-term mild patellar Luxation can often be treated with pain killers and anti-inflammatory medications.  Grade I patellar Luxation cases are most commonly treated in such a way.

 

More severe cases of patellar Luxation (usually Grades II, III, and IV) often require surgical correction.  There are several commonly used surgeries to repair patellar Luxation, and the exact one selected will be determined by a number of factors including the severity of the condition, whether it is present in one or both legs, the underlying cause of the condition, and the direction which the patella moves.  Some surgeries focus on reconstructing the soft tissue around the patella, often loosening the side to which the patella moves and tightening the opposite side.  Other surgeries deepen the femoral grove allowing the patella to move within it easier.  Some veterinarians remove the cartilage entirely to achieve this, but most now remove a wedge or block of both cartilage and bone, preserving some cartilage in the process.  Another commonly practiced procedure transposes the tibial crest, helping to realign the quadriceps, patella, and tendons.  Very severe cases of patellar Luxation may require the entirely femur to be reshaped, especially in instances where a malformed femur is at the heart of the problem.  Such surgeries require pieces of the femur to be removed and reconstructed and a bone plate to be put in.

 

After a dog has undergone surgery to correct patellar Luxation, substantial post-operative care must be provided.  The exact regimen will be determined by the surgery performed and the veterinarian’s recommendation, but owners can expect regular bandage changing, wound cleaning, and anti-biotic provision at the very least.  Depending on the outcome of the surgery, the dog may require additional treatment.  Many dogs require long term pain killers and anti-inflammatory medications, especially if they have developed secondary conditions.  Some dogs may require additional surgical procedures if the first did not prove successful.  In extreme cases, a dog may remain permanently immobilized and may require additional measures such as using a canine wheelchair.

 

Treatment of patellar Luxation is very often successful.  More than 90% of owners are satisfied with the improvements their dogs show after a successful surgery.  Surgeries are less likely to be successful in large dogs or those whose patellar Luxation is combined with other abnormalities.

 

POTENTIAL COMPLICATIONS: 

 

There are a number of potential complications from patellar Luxation and its treatments.  By far the most common is osteoarthritis.  Patellar Luxation, especially if it is chronic, can lead to long-term or even permanent osteoarthritis.  Osteoarthritis can be extremely painful for a dog, and may even partially or completely immobilize it in severe cases.  Osteoarthritis is controllable with medications but is usually not-curable.  Rapid treatment of patellar Luxation will greatly reduce the likelihood of it causes osteoarthritis, but there are no guarantees.

 

Depending on the severity of the patellar Luxation and the amount of time it has been present, a number of other leg deformities may result.  Patellas moving outside of their natural track for long periods of time often rub up against the femur and/or the tibia incorrectly, which can cause serious and permanent damage.  Sometimes this damage actually makes the patellar Luxation worse, leading to a vicious cycle.  The soft tissue around the patella may also be damaged in a similar fashion.  Such damage to the inside of the leg can lead to pain, discomfort, difficulty, moving, and in severe cases total lameness.  The stress put on the legs as a result of chronic patellar Luxation may lead to other complications across the rest of the body such as the hips, spine, and musculature.

 

There are always potential complications from any surgery, including those which may be necessary to correct patellar Luxation.  Some dogs have allergies to anesthesia and may experience anything from a mild rash and difficulty breathing to anabolic shock and death when put under.  There is always a risk that a dog will bleed to death when on the operating table, especially if it has an undiagnosed blood disorder such as Von Willebrand’s Disease.  Other body parts may be injured during surgery, damage which may require additional surgeries to repair.  There is also always a chance that any procedures performed on the dog’s skeleton will result in unforeseen complications and mobility problems later on.

 

HOLISTIC REMEDIES: 

 

There are a number of available holistic treatments for the symptoms of patellar Luxation, although such remedies are not usually able to cure the patellar Luxation itself.  Many holistic healers will be able to manually maneuver the dog’s patella back into its correct place in much the same way as a veterinarian.  However, there are not widely accepted holistic treatments which will prevent the patella from luxating again.  Some evidence suggests that certain types of massage and acupuncture can help reduce the reoccurrence of Luxation episodes, but there is no general consensus.

 

Holistic remedies are often best suited to pain relief.  For example, herbs such as German Chamomile (Matricaria recutita) and Feverfew (Tanacetum parthenium) have been shown to provide significant relief because they act as anti-inflammatories.  Other herbs such as Skullcap (Scutellaria sp.) and St. John’s Wort (Hypericum perforatum) are believed to be highly effective pain reducers or killers.  These treatments are considered most effective for chronic arthritis problems such as the osteoarthritis that can result from patellar Luxation.  Other commonly recommended holistic remedies include cayenne, licorice, ginger, turmeric, and yucca.

 

PREVENTION & HELPFUL TIPS: 

 

Because the vast majority of patellar Luxation cases are genetic in nature, there is not much that can be done to prevent the condition.  Making sure that all dogs are kept reasonably safe from accidents and injuries is all that can be done to prevent those cases of patellar Luxation resulting from physical damage.  Some believe that proper nutrition has an impact of patellar Luxation, but the linkage has not been definitively proven.  It is possible for owners to prevent many complications from arising by early detection and treatment.  The sooner that patellar Luxation is diagnosed and treated, the less likely it is that complications such as osteoarthritis or bone damage are to occur.  Owners should closely monitor their dogs’ behavior, taking special notice of any limping or apparent discomfort, no matter how slight, and report any abnormal behavior to their veterinarians.

 

Although there is substantial disagreement as to the exact inheritance mechanism of patellar Luxation, most experts agree that dogs with patellar Luxation should not be bred in order to prevent the condition from appearing in future generations.  Many experts also recommend preventing any parents, siblings, or offspring of a dog impacted by patellar Luxation from breeding as well, although not all think that this is necessary.  The Orthopedic Foundation for Animals (OFA) has a number of resources, including records of dogs which have been diagnosed with patellar Luxation, for interested owners and breeders.