Facts About Canine Hip Dysplasia
The Hip Joint
The hip joint of the dog is made up of two parts- the femoral head (thigh bone) and the acetabulum (the socket of the pelvic bone). The acetabulum and the femoral head form a "ball and socket" joint. The femoral head surface is covered with a smooth articular cartilage. There is a thin layer of fluid (synovial fluid), which serves as a lubricant for the joint and nourishment for the articular cartilage, separating these opposing surfaces. Muscles encase the entire hip, stabilizing and allowing movement. The head of the femur is held in the acetabulum by the pelvic muscles, joint capsule, surface tension and the round ligament. Proper development of the joint still depends on the head of the femur being held firmly within the acetabulum until all parts are mature.
Dysplasia literally means "bad development". Sometime after birth, something initiates a bad fit or function of one or more parts. What this (or these) initiating factors might be is still not known. It is likely that there are multiple causing factors and they may fodder between genetic lines. CHD is caused by the interaction of many genes (polygenic). Any attempt to define the process in exact sequence is speculative.
In normal dogs there is a smooth and even fit between the femoral head and the acetabulum. In dogs with CHD there is a poor fit of the joint due to abnormal laxity (space between the bone) and/or remodeling of the femoral head and/or acetabulum (changes in bone structure).
The current concept is that CHD is an inherited trait and controlled by the genetic makeup (genotype) of each dog. Genotype is controlled by the genes received from each parent, one half from each the sire and dam. The concept that it is polygenic has been supported by research since the 1960's. Regardless of any changes in theories as to how or why these genes interact with each other as to the mode of inheritance, one thing remains constant. Scientists have repeatedly demonstrated that CHD is controllable with selective breeding.
Signs and Symptoms of CHD
Many dysplastic dogs show observable signs between 3 and 15 months of age, while some can take up to 36 months. This is generally the severest form, characterized by marked pain and lameness. In others, a more chronic form with gradual onset increasingly becoming more affected in advanced age. In some cases the chronic form dog may be asymptomatic. Some of the signs are
reluctance or inability to go up or down steps
difficulty in rising from a sitting or prone position
stiffness early in the day that improves as the dog "warms up"
changes in disposition due to pain
lameness after exercise
wobbly gait or bunny hopping gait when running (moving rear legs together)
painful reaction to extension of the rear legs
Because the hip joint is weakened in a dog with CHD, it is more subject to injury with normal activity such as jumping off the couch or playing with another dog. Often times this results in acute lameness that the owner thinks was caused by the injury, when in fact it is the underlying CHD that has made the joint more susceptible to injury.
Canine Hip Dysplasia cannot be diagnosed by observing how the dog moves, acts, lies down, etc.... The clinic signs may or may not be present and only an orthopedic and radiographic examination can conclude the diagnosis.
Diagnosis of CHD
Radiographic evidence of CHD
The only way to determine the conformation of CHD free or affected is by radiographic examination of the hips. Radiographic criteria of subluxation, shallow acetabulum, remodeling and/or secondary degenerative joint disease (DJD) are well documented. DJD of the hip is characterized by one or more of the following: cartilage damage, joint effusion, synovitis and bony remodeling. DJD is synonymous with osteoarthritis and its radiographic evidence is considered a diagnosis of CHD.
Joint laxity (looseness of the joint) is a dynamic state that cannot be determined by routine radiography. The joint may appear radiographically normal but in actuality be loose.
Laxity is considered to be one of the earliest pathologic findings in CHD. Therefore, demonstration of laxity in young dogs from 3-6 months of age could be a diagnosis of CHD or possibly a predictor of dysplasia. Palpation of the hips is not accepted as a single method of diagnosing CHD. The use of a wedge or fulcrum (placed between the thighs to force the head of the femur out of the acetabulum) is used to determine the degree of radiographic subluxation. Some type of measurement criteria must be employed (Norberg, millimeters, distraction index, etc.) to demonstrate the amount of displacement of the femoral head when compared to a fixed anatomical structure or to a standard radiograph taken without a wedge or fulcrum. The use of the fulcrum has shown that some laxity is expected in a normal joint and that many dogs with laxity beyond a certain point later show characteristic radiographic evidence of CHD.
OFA and PennHIP
The Orthopedic Foundation for Animals (OFA) is a not-for-profit foundation established in 1966. They maintain a dysplasia control registry as a voluntary service to register hip status for Breed club affiliation is an important part of the OFA-By-Laws, as OFA cannot control the frequency of CHD, as they have no control over breeding. Only breeders who wish to use them as a tool can reduce the instance of CHD in a breed.
Radiographs may be submitted to OFA at any age but only dogs 24 months of age or older at the time of the x-ray can qualify for an OFA registration number. Hip status of younger dogs will be evaluated on a consultation report only.
Independent evaluations are done by three veterinary radiologists. These radiologists are concerned with deviations in these structures from the breed normal. Consistency and convergence of the hip joint are considered as well as
2-cranial acetabular margin
3-dorsal acetabular margin
4-craniolateral acetabular margin
6-caudal acetabular margin
7-size, shape and architecture of the femoral head and neck
8-presence of exostosis or osteophytes (bone spurs)
9-subchondral bone eburnation
Each evaluation is independent- meaning that no radiologist knows the interpretation given by the others. These are then compiled into the final consensus.
The consensus report can be one of the following. Excellent, Good or Fair, these are considered within normal range and assigned an OFA number. Borderline is a grade of marginal hips, undeterminable with respect to CHD at this time. Normally repeat films are requested in 6-8 months. Mild, Moderate and Severe are all reports of CHD affected.
It is important to have the radiographs taken by an experienced veterinarian as proper positioning and radiographic technique are essential to accurate diagnosis.
To learn more about OFA, please visit their website at:
PennHIP stands for University of Pennsylvania Hip Improvement Program. In 1983, Dr. Gail Smith a veterinary orthopedic surgeon and bioengineer began to actively research a method for early diagnosis of CHD. The PennHIP was founded as an extension of his laboratory research.
PennHIP is the scientific method to evaluate a dog for it's susceptibility to develop CHD. The radiographic procedure involves using a special positioning to measure a dogs "passive hip laxity". It uses Distraction Index (DI) to measure the maximal passive hip laxity. DI is a unitless number between 0 and 1. A smaller DI means less laxity (tighter hips). The DI has been shown to correlate strongly with a dog's possibility to develop CHD. A DI of .5 is interpreted to mean that the femoral head is 50% displaced from the acetabulum.
The PennHIP method uses 3 different views
Hip-extended Position- this is also known as the standard OFA view. The purpose of this view is to evaluate the hips for existing DJD.
Compression View- during compression the femoral head is pushed fully into the acetabulum. The purpose of this view is to accurately indicate the hips landmarks and to demonstrate congruity....how well the hip fits.
Distraction View- A special "distraction device" is placed between the dogs legs to act as a fulcrum to apply lateral distractive force to the hips. The femoral heads are pushed from the acetabulum to view the passive laxity. This amount is measured using the distraction index (DI).
PennHIP requires a certified PennHIP veterinarian to take the radiographs, and it must be done under heavy sedation or general anesthesia. It is policy that all radiographs taken be submitted to PennHIP for evaluation. This ensures that prescreening of radiographs and only sending the best for evaluation does not occur, resulting in an unbiased data base for the given breed.
To learn more about PennHIP, visit their website at www.vet.upenn.edu
Occurrence of CHD in the Dogo Canario
There are currently no firm statistics on the occurrence of CHD in the Dogo Canario. The original Island breeders did not x-ray their dogs, but relied on the functionality of the dog to determine it's health. Many lines of the breed were established before the necessity of radiographs to determine if CHD was present was well understood. The Club Español del Dogo Canario has conducted a survey of 300 Island dogs to determine the percentage of CHD in the breed. Approximately 12% of the dogs fell into the Excellent to Good (A) category with 22% affected with various degrees.
The majority of the breed fell into the Fair to Borderline (B) rating. They are working towards requiring radiographs on all breeding dogs. In the USA, The Dogo Canario Club of America is working towards that same goal on stock used by American breeders. The Dogo Canario has a typical hip confirmation of a molosser dog with little angluation. At this time the breed averages more subluxation than is typically allowed by OFA examination, resulting in mild ratings on dogs that are otherwise normal. Dogs scoring OFA mild should be evaluated under the PennHip method to get a true reading of their subluxation. Dogs scoring at or under the current breed median, with no DJD, can be considered fit for breeding.
Do not believe any breeder that tells you that CHD is NOT a problem in the Dogo Canario, based on "old history" or "functionality of the dog". It is being reported with more frequency, but usually only when the disease is severe enough to be crippling. Due to the muscle mass and higher pain tolerance of these dogs, they are often asymptomatic until the disease is well advanced, or of the severest form. Investigate the breeders before you purchase. Purchase only from breeders who x-ray their stock and are willing to guarantee your new dog. Ask where the x-rays were taken and who evaluated them? Although many veterinarians are capable of diagnosing an obviously dysplastic dog, not all are as skilled in radiography as a board certified specialist. Ask for written proof of the x-ray results. When your dog is old enough have him/her x-rayed. To date there are only a handful of Dogo Canario dogs even examined by the OFA and recorded into the PennHip database.
Selective breeding is at this time the only tool a breeder has to reduce the frequency in the breed. By breeding normals to normals you increase the chances that a higher percentage of offspring will also be normal. Normal dogs should have normal parents and over 75% normal siblings. But until there is a large enough data base of x-rayed stock breeders can only select those dogs known to be normal.
Possible Treatment Options
Canine hip dysplasia is an inherited genetic disease with a minor environmental roll in its expression in some circumstances. Some environmental factors can influence the expression of the disease and mask or exacerbate the symptoms. Some common factors are:
rough play, jumping, climbing stairs or slick floors
excessive caloric intake during rapid growth phase
forced running for distances, especially on tarmac, asphalt or other hard surfaces
nutrition, illness, trauma, exposure to chemicals
Non surgical methods of treatment for pain management may include, aspirin, phenylbutazone, non steroidal anti-inflamitories, steroids and Rimadyl (Pfzier). All of these drugs should be used under direct supervision of your veterinarian and all but aspirin are by prescription only.
Another product that is showing great promise in alleviation of symptoms is glucosamine. Adequan, Cosequin, Glycoflex are some brand name products which contain this homeopathic substance. Vitamin C is controversial but has been shown to help reduce inflammation.
Reduction in the weight of the dog and a modified exercise program helps to lessen the stress on the dog's weakened joints. An ideal exercise for a CHD affected dog is swimming, which doesn't stress the joints. Keeping the dog mainly indoors and with softer surfaces to lie on will also help to make his life more comfortable.
Surgical treatments are generally reserved for animals for when other treatments offer no relief. There are many surgical options that must be discussed with the advise of your veterinarian. He or she will recommend the best option for your dog.
If your dog is diagnosed with CHD you should notify your breeder so they can evaluate their breeding stock. Without your notification they will be unaware of the problem.
CHD is an inherited disease. It is resulting from the action of many genes, but how many and how they interact is not yet known.
No environmental factors have been shown to cause CHD. They can affect the outcome of expression and/or symptoms, but they in themselves are not the cause.
While it is unrealistic to expect to eliminate CHD in the breed, with careful selective breeding it is proven to reduce the amount of affected dogs. PennHip method has proven to reduce subluxation in some breeds.
CHD cannot be accurately diagnosed by observation or physical examination, nor can a dog be "cleared" by these methods. The only conformation of hip status is radiographic examination.
All dogs have a degree of normal laxity, but increased laxity may be a predictor of CHD development.
OFA and PennHIP are 2 methods of radiographic examination and recording of status that are available to breeders in the USA.
CHD is proven to exist in the Dogo Canario breed, but firm statistics are not yet available.
Choose your breeder carefully and require they are doing the best they can to reduce the frequency of CHD in the breed.
If your dog is diagnosed with CHD, inform the breeder. Treatment options are best discussed with your veterinarian.
Too frequently information on CHD is misleading and may be hazardous. Always check with your veterinarian or nearest veterinary college for the best advise.