Hips and Patellas

Hip Dysplasia

The hip has a ball which is the top part of the femur that fits into a joint hip socket in the pelvis. If the hip socket is loose or not developed correctly the ball does not sit properly. This causes stress on the cartilage lining the hip joint. With the constant stress of movement on the joint the cartilage thins and eventually decreases the joint's ability to handle the daily stress of movement and weight bearing. Over time arthritis can build up in the joint and cause thickening and a decrease in range of motion and accompanying pain.

Hip dysplasia is a congenital, degenerative condition. It is a polygenic disease, which means there are several genes that produce the condition. Environmental factors such as rate of growth, nutrition (e.g. too high protein, excess calcium), excess weight and too much or too little exercise can contribute to hip dysplasia. Certain breeds, primarily larger breeds such as German Shepherds, Golden Retrievers and Labrador Retrievers have a breed predisposition for this condition though it can occur in most dogs, even in smaller breeds such as the Cavalier King Charles Spaniel. The diagnosis of hip dysplasia is made by x-ray. These can be done in the Cavalier without anesthesia for the most part.

 The Orthopedic Foundation for Animals (OFA) estimates that in excess of 12% of Cavaliers have various degrees of hip dysplasia. This is based on the hip x-rays that are voluntarily submitted to them for review by their radiologists. There are a number of organizations that review radiographs. Two of the most popular are OFA and PennHIP.  

 Hip x-rays submitted to OFA are reviewed by radiologists and given the ratings of Normal (Excellent, Good, Fair) Borderline, and Dysplastic (Mild, Moderate, Severe).  OFA then sends the owner a certificate with the results and it is also recorded on the OFA website. 

PennHIP uses a series of three x-rays that measure the amount of laxity found.  PennHip publishes the average scores for each breed and suggests that only dogs that have a certain range be used for breeding. 

Submission of hip x-rays are one of the four requirements to be given a CHIC (Canine Health Information Center) number.

 

As this is a degenerative disease, it is recommended that breeding dogs be restricted until after the age of 2, and until they have been x rayed for evidence of the disease. An affected dog should never be used for breeding. As with many other inherited diseases while x-raying may indicate that the individual does not have signs of hip dysplasia, it does not answer the question of whether a dog is a carrier and can pass the condition to its offspring. You do however increase you chances of good hips by selective breeding.

 

If a dog is diagnosed with hip dysplasia, depending upon the severity of the condition, treatment varies from dog to dog. It is also helpful in controlling the symptoms of hip dysplasia, to keep the dog's weight down as the excess weight puts more strain on the hips.

 

Patellar Luxation

Toy breeds are very prone to medial luxating patellas.

Medial patellar luxation is most common in Poodles, Yorkshire Terriers, Pomeranians, Pekingese, Chihuahuas, Miniature Pinschers, Boston Terriers and Cavalier King Charles Spaniels. Females have the highest risk for this condition. Laterial luxation can also be found in younger large and giant breeds and older toy breeds.

Diagnosis is relatively simple for a veterinarian familiar with orthopedics. It involves palpation of the joint and manual luxation of the patella. Care must be exercised with the examination to avoid injuring the joint, or making an incorrect diagnosis. Patellar luxation may be classified in four grades, with grade 1 being the mildest. This grading system is subjective so it is important in the presence of luxation to have the same veterinarian perform the follow-up screening. Mild patellar luxation (grade 1-2) may be discovered as an incidental finding especially in a growing dog or a female in season. In addition, patellar luxation may occur in any breed because of trauma.

Patellar luxation (also called slipped stifles/kneecaps) results from abnormalities in the bones of the rear legs, such as a shallow trochlear groove. This condition is easily checked by manipulation by a veterinarian. Patella luxation is graded into 4 degrees of severity. The four degrees are:
 


Grade 1 - the stifle joint is almost normal and luxation is found on examination. Usually there is no gait abnormality.


Grade 2 - the patella lies loosely in its normal position but will luxate when the joint is flexed. Dogs with a Grade 2 may have a "bunny hop" gait where the patella moves out of the trochlear groove and the dog hops along on the good leg trying to kick the bad leg straight to move the patella back in place.

Grade 3 - the patella is dislocated much of the time but can be manipulated back into the joint when the leg is extended.


Grade 4 - the patella is dislocated all of the time and needs surgery to correct.


In both Grades 3 and 4 the dog shows varying degrees of lameness, often with a bowlegged appearance with the toes pointed inward due to the deformity of the rear legs.

Pain is usually not associated with this condition unless it is the result of trauma or until degenerative arthritis has occurred due to chronicity of this condition.

The treatment and long-term outcome (prognosis) depends on the severity of disease. Severity is determined by how often the kneecap slips out of place, and how easily it slips back into the normal position. Treatment is based upon severity of signs and the affected dog’s age, breed and weight. Conservative therapy (non-surgical) and veterinary observation is often the treatment of choice; however, if the patellar luxation causes persistent lameness, or other stifle/knee injuries occur secondary to the luxation, then surgery intervention needs to be evaluated.

Dogs used for breeding should have the examination submitted to the Orthopedic Foundation for Animals (OFA) stating “within normal limits” patellas. This is one of the four requirements to receive a CHIC (Canine Health Information Center) number.


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