An honest discussion about Hip Dysplasia in Labradors

I recently was visiting a Labrador Forum where yet another Lab from OFA tested parents had just been diagnosed with dysplasia. Nestled in amongst all the replies from forum members expressing their condolences was one post that jumped out at me.

“Why are so many Labradors STILL being diagnosed with hip dysplasia even though their parents were OFA certified?”

Over on another thread I saw this:

"I would NEVER buy a puppy whose Sire or Dam had a fair result from the OFA on their hips!"   

and then this:

"MY breeder gave me a warranty on my puppy's hips and elbows and I will get my money back if my dog gets dysplasia". 

Before our Angus was diagnosed with dysplasia, I might have said the same as those last people. I know for sure that I THOUGHT the same. After all, I had chosen a breeder whose Bitch was certified “Excellent” on her Hips who had chosen a Stud who was also “Excellent”. And Angus’ breeder gave me a health warranty good for two years on Angus’ own hips. I had done everything possible to ensure that I didn’t have a Labrador who would suffer from HD. Right? 

The answer is no. The honest answer anyway.

It is the honest answer because there is currently NO genetic test that can be given to ensure that two Labradors will not ever produce a puppy that will develop dysplasia. Despite decades of searching for a "gene" that would identify which dogs will get dysplasia, one has not been found, nor has any combination of genes been deemed as responsible (there have been reports that STR's and SNP's - in the thousands - have been suspected of causing dysplasia, but as of now, no genetic test is available).

So breeders rely on subjective readings of x-rays and certification of those x-rays to determine which dogs might increase the odds that puppies will NOT develop dysplasia. Six decades past and then again twenty-two years ago, Breeders were asked to be patient and allow several generations of selective breeding to eliminate canine dysplasia, we are still waiting. Journal of the American Veterinary Medical Association 210(10):1474-9 · May 1997

No is also the honest answer because I did not provide the proper environment for Angus. I over fed him and over exercised him. I allowed him to play on stairs, jump as often as he wanted, allowed unsupervised play with older dogs with more aggressive play styles. I allowed the OFA certification of his parents and a breeder's health warranty to give me a false sense of security. Although his breeder honored the Hip warranty and refunded our purchase price, that was little consolation to me as I watched 10 month old Angus struggle while we found the tools to manage his pain.

The heartbreak of Angus' diagnosis at 10 months of age with mild dysplasia in one hip, moderate in the other, and elbow dysplasia at 18 months sent me researching to help prevent this happening to any other dog I brought home or sent home to another family. I rather quickly found that the trust placed in those OFA certifications and Hip and Elbow Warrantees had led other owners of Labradors to experience that same heartbreak and guilt. 

Far too many Breeders and Pet Owners believe that phenotypically testing the breeding dogs means that their dogs will never develop dysplasia; many a Breeder has been forced to refund the purchase price or exchange a puppy because of state laws or warranties that put far too much faith in what is essentially a failed experiment to see if we can eliminate dysplasia. And many an Owner, like me, believed that because their dog was the offspring of generations of selectively bred dogs and came with a warranty for hips and elbows, we and our dog was safe.  

The reality is this, 60 plus years of choosing our breeding stock based upon the certifications for their hips and elbows has NOT eliminated dysplasia.  It is NOT found primarily in dogs from breeders who don't certify or from back yard breeders and pet stores.  

Breeders can improve the odds for puppies but cannot prevent the disorder entirely because a determination of "Normal" Hips and "Normal" Elbows by the Orthopedic Foundation for Animals does NOT eliminate the risk for the offspring and along with Breeder Health Warrantees, provide a false sense of security to far too many Labrador owners.

Dysplasia is on average 30% a GENETIC PREDISPOSITION and 70% Environment.  

"Although there is a genetic influence on hip dysplasia, the heritability of the trait is rather low. Many studies have shown that genetic variation accounts for only a modest fraction of the variation in hip scores, usually 15-40%. (Breed dependent which accounts for the range)"Most of the estimates of heritability of hip dysplasia score in dogs are in the range of 0.2-0.3, which means that 20-30% of the variation you see among dogs in hip scores is accounted for by genetics - and it also means that 70-80% of the variation is from environmental causes, many of which breeders and owners can control."  Institute of Canine Biology Heritability by Carol Beuchat PhD, ©2014 

While no one can deny that there is a upward “trend” in the number of Labradors certified with “Excellent” hips and an apparent downward trend in those certified as dysplastic, one has to acknowledge that this is shown almost exclusively in dogs owned by breeders and to question how much of that is a result of breeders education and experience in reading x-rays prior to sending them off for certification AND in carefully raising the dogs for the first 12 months - 2 years by providing an environment that protects hips and elbows during the rapid growth phases.

And more thoroughly educating Pet Owners on the importance of the environment they provide their growing Labrador puppy will no doubt lower the incidence of dysplasia - as Breeders, we need to warn our buyers against a false sense of security provided by OFA testing and our warranties.

Together, Breeders and Buyers can tackle this issue of dysplasia in our Labradors. By understanding that despite the emphasis put on certifying breeding dogs for "normal" hips and elbows for more than six decades, the fact that we have NOT eliminated it through selective breeding proves that the disorder is more a genetic predisposition triggered by environment and nutrition than an "inherited" disorder, we can help protect every puppy from every litter.  

Obviously, there is more to dysplasia than we have been led to believe, so let's dig deeper.

First, let's look at some important points that most pet owners and far too many Breeders are unaware of:

1. "Selectively bred" Definition: Selectively bred dogs are those chosen by breeders based upon a variety of reasons - conformation to the breed standard, temperament, drives and traits, genetic health testing for disease and phenotypical testing (X-rays and evaluation of those) for hip, elbow and patella health. These are the dogs who are represented as the majority in any breed found within the databases of the OFA. 
   
2. "Pet population" Definition: The pet population consists of those dogs not selected for a breeding program who are never phenotypically evaluated for dysplasia and those who are due to lameness whose results will never be sent to the OFA. 
   
3. 67% of selectively bred Labradors tested by the OFA are "GOOD" "FAIR" or "BORDERLINE" after more than 60 years (30 generations on a dog's pedigree) of selectively breeding OFA certified dogs. Dysplasia has not been eliminated as breeders and owners were promised. 
4. The Pet Population is grossly under represented in the OFA Database where 12%- 14% of selectively bred Labradors are still rated with varying degrees of dysplasia. OFA TRENDS REPORT FOR LABRADOR RETRIEVERS
5. Originally, the OFA certified hips at 18 months but when selectively bred dogs were still being diagnosed with dysplasia, they changed certification age to two years. The next step was to divide the "Normal" results into three categories in an attempt to show improvement beyond what Breeders were promised. Still, today, the offspring of selectively bred dogs are being diagnosed with dysplasia. 
6. The Founder of the OFA, the man who initially believed that phenotypic testing of breeding dogs would eliminate dysplasia resigned when he realized that this was not happening.  Regardless, the OFA continues to set the criteria for choosing our breeding dogs and Breeders, despite doing all they were asked to do, are still liable for offspring that were crippled by the disorder.

Continually moving the goalpost has not eliminated dysplasia because - as studies are proving - it is not "inherited" from parent to child as much as it is a genetic predisposition shared by all medium and large breeds based upon structural and temperamental TRAITS of the breeds themselves.  More about this in a bit. 

NORMAL Hips are rated as Excellent, Good, or Fair but ALL are considered normal. The variance is in slight changes to the joint. The OFA reports that 19% of over 270,000 OFA tested Labradors are ranked as Excellent. OFA doesn’t report the percentage of Good and Fair ratings although the dogs are given a certification number.

BORDERLINE Hips means the dog does NOT have dysplasia but has changes that indicate that it may develop later onset dysplasia / arthritis. Again, OFA doesn’t report the percentage of dogs that receive this rating.

DYSPLASTIC Hips are rated as Mild, Moderate, or Severe. The OFA reports that 12% of over 270,000 OFA tested Labradors are “dysplastic”. (Again, it doesn’t report the percentage of mild, moderate, severe or even bilateral or unilateral results.) 

Note the difference is how "Normal" is reported (only the percentage of Excellent is given) and how Dsyplastic is reported (the categories are combined rather than using only Severe). This method of reporting the Breed Trend leaves us with the following information - 67% of Selectively Bred Labradors Retrievers are not Excellent or Dysplastic.  What are they?  Borderline?  Is Borderline the normal state of a selectively bred Labrador's hips?

There are two levels of testing performed. A preliminary (primarily done to determine if a dog will certify as normal to re-home as a companion if the dog fails OR to breed a bitch at the heat nearest her second birthday) and final certification at two years of age. There is a greater than 90% probability that a Normal result at 18 months will be the same at 24 months. (The 24 month requirement for certification is an arbitrary decision based upon the recommended breeding age of bitches.)

Preliminary (before the age of two years) X-ray of hips is read by only one radiologist. 

Final certification (after the age of two years) is read by three radiologists.  Once each of the radiologists classifies the hips into one of the 7 phenotypes above, the final hip grade is decided by a consensus of the 3 independent outside evaluations. Examples would be:

• Two radiologists reported excellent, one good--the final grade would be excellent
  
• One radiologist reported excellent, one good, one fair--the final grade would be good
  
• One radiologist reported fair, two radiologists reported mild--the final grade would be mild
  

Note that

• Three Radiologists can all see the same X-ray and have different opinions.
  
• A resubmitted or new x-ray will sometimes have a different result when seen by different Radiologists and sometimes, even the same one or more
  

A genetic predisposition is a genetic (unseen) characteristic, which influences the possible phenotypic (seen) development of an individual organism within a species or population under the influence of environmental conditions. 

The AKC acknowledges this in the following statement:

“Factors such as excessive growth rate, types of exercise, and improper weight and nutrition can magnify this genetic predisposition” (to dysplasia).

Hip Dysplasia in not "inherited" in the way that automatically comes to mind when one reads that word. Although it said that dysplasia is "inherited", the reality is more likely that that inheritance is because of traits of the breed rather than passed from a parent to offspring; in other words, every Labrador has the potential to develop dysplasia and how they are raised will in the majority of cases, determine whether they do or not. Even dogs certified as Excellent at two years of age may STILL develop late onset dysplasia. 

Rate of Growth: The average Labrador weighs about 1 pound at birth; they double their weight by 2 weeks of age and by 8 weeks weigh on average between 12 and 16 pounds. By 8 months of age, they are nearly at their adult weight which can be anywhere from 65 to 100 pounds and are at about 80% of their adult height. All parts of the Labrador do NOT grow at the same pace which creates weaknesses in areas that may lead to injury which may lead to issues within the hip joint or elbow - an injury in one leg affects the gait of other legs increasing the odds of joint issues in a second leg.

Temperament traits: Labradors - especially as puppies - are high energy, high drive dogs. When they play, they play full out. When they run, they run full out. This high energy continues until they are at least 2 years of age and with some Labradors, until they are 3 years of age! Many owners will seek to find outlets for this high energy that are inappropriate for the growing puppy – excessive leash walking on hard surfaces like pavement; excessive retrieving where the puppy is jumping to catch a ball, stick or frizz bee; activities like agility training where consideration is not given to age appropriate training – all are contributors to the development of dysplasia. Bred to retrieve game in freezing water temperatures, they have a high pain tolerance and don't always show they are injured exposing them to the dangers of repeated trauma to a vulnerable area. The puppy that jumps up on doors, fences, and windowsills, on and off of furniture and in and out of vehicles is experiencing repetitive trauma to joints.

• Estimated heritability of an average of 30% (reaching 50% in well designed studies) - Page 137

• Most of the estimates of heritability of hip dysplasia score in dogs are in the range of 0.2-0.3, which means that 20-30% of the variation you see among dogs in hip scores is accounted for by genetics - and it also means that 70-80% of the variation is from environmental causes, many of which breeders and owners can control.

• Although there is a genetic influence on hip dysplasia, the heritability of the trait is rather low. Many studies have shown that genetic variation accounts for only a modest fraction of the variation in hip scores, usually 15-40%. (Breed dependent which accounts for the range)

• "Hip dysplasia (HD) in dogs is affected to a larger degree than previously believed by the environment in which puppies grow up. It is particularly during the period from birth to three months that various environmental factors appear to influence the development of this disease. During the puppy stage, preventive measures can therefore be recommended with a view to giving dogs disposed to the condition a better quality of life. Dogs are not born with HD, but genetically disposed puppies can develop varying degrees of HD.”

• Hip dysplasia (HD) and elbow arthrosis (EA) are, despite extensive breeding programs, still causing problems in many dog breeds such as the Labrador Retriever. Among the environmental factors involved in developmental bone diseases, experimental studies show that overfeeding has proven to be detrimental in both hip (1–3) and elbow dysplasia (3). Over-supplementation of calcium has been shown to be a risk factor for osteochondrosis, one of the main constituents of EA, in both experimental (1) and epidemiological studies (4). In an epidemiological study published in 1992, Slater et al. (4) found that playing with other dogs might also be a risk factor for osteochondrosis dissecans in dogs.

• However, conformational characteristics and environmental factors such as diet and exercise are thought to have profound effects on the phenotypic expression of DJD in individuals genotypically predisposed to hip dysplasia.

• OFA rankings of breeds - Labrador Retriever ranked 98th in Breeds with dysplasia

• The #1 and #2 common injury factors for puppies - it's not just about hips and elbows

• Neutering Dogs: Effects on Joint Disorders and Cancers in Golden Retrievers Published: February 13, 2013

• Environmental Factors Can Affect the Incidence of Hip Dysplasia Posted Date: February 11, 2013

• Diet, Exercise, and Weight as Risk Factors in Hip Dysplasia and Elbow Arthrosis in Labrador Retrievers Marie H. Sallander Åke Hedhammar Mari E. H. Trogen The Journal of Nutrition, Volume 136, Issue 7, July 2006, Pages 2050S–2052S

• Calcium and Phosphorus

• Dog Food Standards by the AAFCO