Types of Canine Hip Tests
- Kenwood Retrievers
- May 30, 2024
- 13 min read
What is Hip Dysplasia?
Before we can compare the different types of hip screenings in dogs we must first understand why hip screenings matter. Hip screenings are often done as a preventative test for understanding a dog’s likelihood of developing hip dysplasia later in life. Hip dysplasia is a medical condition that affects more than 15% of dogs, a number that is closer to 21% in working and hybrid dogs. The greater risk that large dogs have to develop hip dysplasia places an increased importance on testing their hips.
A dog's hip is located at the top of their back leg, this joint consists of the ball (femoral head) and socket (acetabulum) of that leg. The joints of their front legs are called their elbow. Dysplasia is when something doesn’t develop properly. Think of it like a Dys-Placed Hip. Dysplasia can happen when the bones and ligaments around the hip joint don’t form together as they should. When one or both of the hips develop abnormally and don’t attach well to the socket it causes friction on the joint. This is called hip dysplasia which leads to discomfort with movement, and over time can lead to painful osteoarthritis. There are a variety of ways in which a dog's bone structure can be malformed. Any deformity in the bones is called primary osseous dysplasia, which is when the femoral head or acetabulum is not formed correctly. The other form of Hip dysplasia is a dysplasia of the ligaments called soft tissue dysplasia. Both forms of dysplasia are often a hereditary condition, but environmental factors also play a huge role.
Sadly treatment for hip dysplasia is expensive and invasive, hip replacement surgery can often cost several thousands of dollars. Limiting the pain of dogs and reducing the financial burden of this disease is a big goal of responsible breeders. There are a few factors that contribute to whether a dog will develop hip dysplasia, genetics, nutrition, and other environmental factors like exercise are a part of the equation. However, while environmental prevention is mostly up to the puppy owner, the breeder can do a lot to limit hip dysplasia genetically. For breeders, hip screenings are helpful in the process of securing the best genetics for their puppies. There are four different testing organizations that breeders can use to test for hip dysplasia in their dogs.
How Do Hip Screenings Help Prevent Hip Dysplasia?
Hip screenings or tests take X-rays of a dog's hips. These X-rays are then sent to experts to be reviewed for the likelihood of the disease and given a rating. With the rating given, breeders must decide whether the genes of their dogs are worth reproducing. While dogs with extreme hip dysplasia start showing signs as early as a couple of months old, dogs that have a milder case may not show signs until they are several years old. If a breeder were to start breeding when their dogs were sexually mature, between 6-24 months, and that dog unknowingly had hip dysplasia, they could have several litters before that dog would show symptoms at 5 years old. This would mean that anywhere from 10-100 puppies could have hip dysplasia as a result of that breeder reproducing a health condition without knowing it. Unless the dog has an extreme enough condition to show signs early in life, the breeder will be blindly guessing when they breed their dog if they have not tested for hip dysplasia.
Hip screenings are usually done at around two years old. This is one of the reasons responsible breeders will wait until the dog is two years old to breed. Since Hip dysplasia is such a prevalent issue in many breeds of dogs, working toward weeding out the genetic variants of this disease is one of the ways a breeder can improve the breed. Hip screenings are one of many health screenings that breeders should perform. The Orthopedic Foundation of America (OFA) offers a list of recommended tests for each breed on its website.
Hip testing is recommended regardless of their breed. Doing hip screenings through OFA or one of the other organizations is one of the best ways a breeder can prevent hip dysplasia in the puppies they produce.
The other advantage of hip screening, especially for young dogs, is a preventative measure for the dog itself. When hip dysplasia is detected in a young dog the owner and vet are able to take steps to limit its impact on the dog. The younger this can be shown on a dog the easier it is for surgical or other interventions to be taken to mitigate potential pain for the dog. This is one of the advantages of PennHIP since hip dysplasia can be shown as early as 16 weeks. While the other tests require a dog to be at least 12-24 months before like this can be done.
How Are The Screenings Performed?
To perform these X-rays a dog is laid on its back, and is sometimes sedated to ensure complete relaxation. The dog's legs are extended downward and rotated inward. Veterinarians take at least one x-ray of the animal's hips and pelvic bone, like the graphic to the right. This picture is then sent to the respective organization for evaluation by experts. These veterinary radiologists called scrutineers then review the images for deviations from what is normal in the breed. They are trying to determine whether or not the dog has or will later develop osteoarthritis based on any hip abnormalities. A good hip is tight and the ball fits well in the socket. Any variation in the bone structure or joint laxity can over time cause painful arthritis. There are various methods of interpreting an X-ray to try to predict if the dog will later develop hip dysplasia.
What Are The Different Testing Organizations?
Four different organizations offer hip screenings. While they all share the goal of reducing canine hip dysplasia through evaluating radiographs, there are a variety of ways in which these X-rays are interpreted. The scrutineers use very different methods to detect hip dysplasia ranging in objectivity. Some tests rely more heavily on the expertise of the scrutineers while others place the ethos on a mathematical equation.
OFA Orthopedic Foundations of America
History: OFA hip testing is the most common in the USA and is the most standardized form of testing. It is a non-profit started in 1966 by John M. Olin. While they offer evaluations for a variety of different medical issues, they were initially started to minimize hip dysplasia. They have a large, easily accessed online database and continue to research critical health issues in dogs.
Method: One Radiograph is sent to 3 Board Certified veterinarian radiologists separately to evaluate based on their understanding of the X-rays. They consider the age and sex of the dog and determine how normal the hip looks for the breed. They look at 9 different points in the hip joint for any abnormalities from the breed type, as well as the tightness of the ball and socket. Each scrutineer individually gives the hip a rating and the ratings of all three scrutineers are combined to give the official result. Resubmissions are allowed to be sent in and are recommended if “Borderline” is the result given.
Results: When you submit radiographs to OFA you will receive one of the following scores, from the 3 experts reviewing them: Severe, Moderate, Mild, Borderline, Fair, Good, and Excellent. These results are pretty straightforward to understand. According to OFA Severe, Moderate, and Mild, are considered abnormal results and should not be bred. Borderline results should be retested at a later date. Many breeders, in an effort to improve the breed and not just maintain the current Hip Dysplasia statistics, would not breed a dog with a "Fair" rating. Though this may vary by breed.
FCI Fédération Cynologique Internationale or International Canine Federation
History: FCI is an international dog registry similar to the AKC (American Kennel Club). Their goal is to create a standardized breed standard and testing worldwide aiding international dog breeding. This is especially important in places like Europe where the breeder population is smaller in each country and more genetics are shared across nations. The FCI is also the main health screening organization in Europe. They work with national clubs for both breed standards and health testing, which is why some requirements vary by nation. It is important to understand how the FCI health testing works even if you are in the USA, especially if you are considering a line of dogs that have been largely imported dogs, like the English Golden Retriever.
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Method: One scrutineer, depending on the country, will review the one to two X-rays submitted. FCI uses the Norberg Angle (NA) to help objectively evaluate dysplasia. The NA is usually calculated by a software, in which the diameter of the Femoral Head or Ball is drawn. A line between the center of the circle is drawn to the cranial effective acetabular rim (roughly the top of the socket from the view of a radiograph). When this is done on both hip joints a line is also drawn connecting the center of both circles. Each hip has a calculated angle from this measurement. The wider the angle, and the higher the degree the less the ball is out of the socket. Each rating the FCI gives has a minimum angle that is allowed for each rating. FCI Also looks at different points in the joint and compares them to written descriptions of correctness.
Results: Of the two hip joints evaluated, the one with the lower score that meets the written criteria of an A, B, C, D, E will have the rating that stands. An “A” Hip has excellent conformity to the written standard of what a good hip should be. A “B” is slightly less perfect, while a “C” Hip can show signs of osteoarthritis. A “D” or “E” Hip can have the ball well out of the socket and be dysplastic. Different breeds and countries recommend what ratings should be bred. Since the FCI is also the registry organization, they have the ability to require hip testing for a dog to be bred, though only a few countries take advantage of this.
BVA British Veterinary Association
History: BVA is an organization that exists to support veterinarians in various fields of work. They were founded in 1919 and are the largest Veterinary community in England. This Testing organization is gaining popularity throughout Europe and dogs outside of England are often tested through this organization.
Method: Two certified radiologists or orthopedic scrutineers work together to evaluate a radiograph. The BVA uses a combined evaluation method of the Norberg angle (see FCI method), a written description of how much subluxation is allowed, and the position of other points in the hip joint.
Results: Once the scrutineers have agreed on a rating of each individual hip, that hip is rated between 0 and 53, with a combined score of 0 to 106. The lower the total score the less likely the dog will develop dysplasia. Using these Hip scores can be a bit more complicated than OFA or FCI. The BVA recommends taking the score and comparing it to the breed median for hips and only breed dogs that are at or below the median.
AIS PennHIP Antech Imaging Services Penn Hip Improvement Program
History: PennHIP is the newest screening on the scene. Dr. Gail Smith as a part of the Penn veterinary program developed a different type of method to help prevent Hip Dysplasia. This unique method enables Vets to be able to screen puppies as early as 16 weeks.
Method: PennHIP stands alone in the way the radiographs are evaluated. Instead of selecting people from a panel of experts to scrutinize the image, the radiographs themselves are measured. Three radiographs are taken with the dog's hips in different positions. They then measure how far out of the socket the joint is. This is called the Distraction Index or DI. The further the ball is out of the socket the more laxity that joint has. Since the level of laxity is directly correlated with the likelihood of developing osteoarthritis, it is deemed sufficient to grade based only on this measurement. As seen to the right the distance between the center of the ball and the center of the circle is divided by the radius of the femoral head.
Results: Interpreting the results of PennHIPs is the most complex to understand. Similar to BVA, you are given a number instead of a word or letter grade. The number corresponds with the Distraction Index. Scores given are between 0-1. The lower the number received the less laxity there is in the hip. Therefore a perfect score would be a 0. The higher the number, the further the ball is out of the socket, 1 is the worst score you could receive. Each hip is measured separately but the hip with the worse score will be the one you receive. Along with the number you receive, you will also get a chart showing how your dog's number compares to others in the breed and the likelihood that it will develop osteoarthritis. Scores below .3 are unlikely to develop dysplasia, while scores that are close to 1 are likely to develop dysplasia. The number that you are given is compared with the ever-growing database at the time of the screening. The chart you receive shows you how your dog compares with others of the breed, graded on a curve. The chart provides the average score of the breed. As well as a Gray strip showing you where 90% of the dogs in the breed fall. And the percentage of dogs to which your dog's hips are better or worse than that breed. If you have a dog with bad hips the score may say that your dog's hips are worse than 80% of the breed. If your dog has good hips, it may say that your dog’s hips are better than 75% of the breed. The recommendation on whether or not to breed a dog is also breed-specific.
Other Little-Known Testing Organizations
There are a few other Hip screenings organizations. One is SV (Verein für deutsche Schäferhunde), a German Shepard Registry in Germany. Understanding this organization may be important if you have a German Shepherd. Switzerland, the Netherlands, and Canada have also offered health screenings in the past. As these organizations no longer have hip screenings available, their data is only important if looking at older pedigrees.
How The Organizations Compare
The primary way that breeders determine which organization to send their radiographs to is according to their country of residence. Most organizations however accept radiographs from other countries. For example, it is possible to be living in America and send radiographs to the BVA. Location however is one of only many factors contributing to the differences in the organizations. Breeders should take thought of the most reliable form of scoring for the most trustworthy way of determining how likely their dog is to develop dysplasia. Numerous studies have been done to this end. Some suggest OFA as the least objective method and not as trustworthy. Other studies highlight the importance of a fully developed dog if the tests include the shape of the hip joint. Since FCI and BVA only require a dog to be 12 months old, they are shown to be less reliable, since and the hip joint isn't developed. Still others compare the Norberg Angle to the Distraction Index, suggesting that the Norberg angle though more objective than OFA, is not as accurate as the Distraction Index. Cost, number of scrutineers, number of dogs in the database, whether the breed registry accepts the results, and other factors may influence a breeder's decision on which organization to send hip screenings.
How can Breeders improve the Breed Using Hip Scores?
Do your research! Read the studies available and compare the different organizations. Remember the goal isn’t just to get the bare minimum score and get on to breeding. Responsible breeders should be seeking to improve the breed. This may mean traveling to a vet that can perform a different type of hip screening. Or redoing hip screenings that were done at a young age in a different country. Know how to interpret the results. If your dog’s hip score is below the breed average, understand how far below, and how big of an issue hip dysplasia is in your breed. Not all organizations are the same, but at this point doing any one of the four offered is sufficient to make improvements in each breed's development.
Why not only breed dogs with perfect Hip Scores?
This is an honest question asked by breeders and puppy buyers alike. The problem is that breeders have more goals for their dogs than just perfect hips, like good temperaments, intelligence, dogs that at least resemble the breed type, and hopefully would do well in a show. There are even more health concerns for dogs than just their hips, heart, ears, elbows, backs, eyes, and skin, just to name a few. If it were even possible to boil all these factors down to mere numbers you would be left with some high and some low stats in every dog. The wonderful science that brought you to those stats would leave you staring at a juxtaposition of a perfectly imperfect dog. The sweetest dog may rank it at a 10 for personality, but with very slanty eyes, and crow's feet, ranking its conformation near a 3. Would you breed this dog? What if it had amazing hips? What if it had slightly below-average hips? What if it’s prospective mate had perfect feet and hips, but the same slanty eyes and was kind of timid? The answers to these questions are not quantifiable by science. They lead us to what is called the art of breeding. It is in the art of breeding that a breeder takes everything good and bad known about the dog and decides if it has qualities that are worth reproducing. If the dog's good qualities aren’t outweighed by major faults the breeder will seek a mate that improves upon the faults. The art and science combined in this mating creates puppies with a genetic makeup that God only knows.
What should Puppy Buyers be Looking For?
Make sure the breeder is doing hip testing! Know how prevalent an issue of hip dysplasia is in your breed. If it is a major concern as it is with most big dogs, then hip testing should be taken very seriously. Buying a puppy from parents with above-average (for the breed) hip scores is the best way to prevent your puppy from developing dysplasia. Depending on the breed hip dysplasia may be only a minor concern, and in those breeds it may be sometimes acceptable to purchase a puppy from a parent that has a lower hip score. In no case, however, should you buy a puppy from parents who have hip dysplasia. When you are searching for a breeder who does hip testing, make sure you can see the results for yourself. Not all breeders post results online because of safety concerns, if they aren’t posted ask for a copy of the tests. It is good to remember that even a puppy who comes from parents with perfect hips does not mean that it can't develop hip dysplasia. As the puppy owner, it is your responsibility to provide a good diet for the puppy and not over-exercise the dog as their joints develop.
A Personal Note
The health of our dogs and their progeny is one of the major pillars of our breeding program. Hip testing is no exception. This is why all of the dogs that are a part of our breeding program have been tested with PennHIP. As the most objective test out there we feel it has the best chance of improving Golden Retriever genetics. We also have all of our dogs tested with either OFA, FCI, or BVA so that they can meet the requirements of their breed registries, and their data can work inside those organizations to help improve the breed as well. All of our breeding dogs also have scores that are above the breed average. As a breeder with primarily imported dogs many of our dog's parents have been tested with BVA or FCI. While we feel strongly about the importance of PennHIP, we also recognize that not all of the dogs in our dog’s lineage will at this time be able to be tested with PennHIP. Perfection isn’t always possible but gradually working toward that is what we strive for.
Further Sources
Prevalence of Canine Hip Dysplasia https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5366211/#:~:text=The%20hip%20dysplasia%20scores%20were,overall%20CHD%20prevalence%20of%2015.56%25.
DI compared to Norberg Angle
OFA, BVA, FCI Comparison
OFA compared to PennHIP
PennHIP further study antechimagingservices.com/antechweb/pdf/AIS-PennHIP-Manual.pdf
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