Understanding Hip and Elbow Dysplasia

Because there is a tremendous amount of bad information, misinformation, and misinformed vets, I want to share some truth about dysplasia. This is an issue in more than just the Rottweiler breed. Please research before you purchase a puppy, if any breeder claims that they know 100% your puppy will never develop this issue then they are A. Mis informed or B. Lying. An ethical breeder will know about health issues related to the breed and have an understanding of how they are inherited or develop. We are not Gods, we work in percentages with genetic possibilities and can not control with absolute certainty whether a dog/puppy will develop dysplasia at some point in its lifetime. Environment, poor diet, exercise, normal play, injury, and the list goes plays a huge role. For those who still believe that hip/elbow dysplsia is controlled solely by getting hip/elbow evaluations here is an excerpt from the Institute of Canine Biology "After more than 50 years of research, we still don't know the all the causes and we haven't found the genes." Which backs up what I have been trying to educate people on for quite some time now, it is a polygenic inheritance, meaning multiple genes come into play to allow for a pre-disposition to develop dysplasia, NOT an absolute. Definition of polygenic pol·y·gen·ic (pŏl'ē-jěn'ĭk)
adj.
Relating to a characteristic or disease controlled by the interaction of genes at more than one locus.
It is important to have our breeding dogs evaluated because you should never breed a actively dysplastic dog, but even by doing so that still does not eliminate the possibility that offspring from breeding cleared adults will not result in dyspasia. Many factors come into play for the development of dysplsia not just genes alone. 

By Carol Beuchat PhD

The risk of developing hip dysplasia is closely related to hip laxity, which is the degree to which the head of the femur can be displaced from the hip socket. In a normal dog, the head of the femur fits snugly into the cup that forms the socket (acetabulum) of the hip joint. In a dog with dysplastic hips, the acetabulum is deformed and shallow, the fit with the head of the femur is poor, and subluxation (partial dislocation) of the hip is possible.
Hip laxity appears to be a necessary condition for the development of dysplasia or degenerative joint disease (DJD). However, there are differences among breeds in the probability, timing, and degree of development of DJD. 

 In the Rottweiler (top graph), for a DI = 0.75 (on the horizontal axis), there is a 50% risk of DJD by the time the dog is 35 months old, and 50% of the Rottweilers with a DI = 0.95 will display DJD by the time they are 16 months old. The greater the DI, the earlier in life the dog is likely to display signs of degenerative joint disease.  

The bottom line here is that breeds vary in their sensitivity to hip laxity in the development of degenerative joint disease. A Labrador Retriever with a distraction index of 0.5 has a low risk of DJD by 24 months (about 10%), while the same DI for a GSD is associated with a 40% risk of DJD by the same age. A DI of 0.5 presents a relatively low risk of DJD in a Rottweiler or Golden Retriever (about 10%), but a significant risk (40%) in a GSD.

This means that interpretations of hip scores need to be breed-specific. This is highlighted as well in a study of breed-specific differences in hip laxity in smaller breeds. This graph shows the distraction index (vertical axis) for 15 breeds of dogs weighing from 4-16 kg (8-35 lb). This study focused on dogs with normal hips that were free of any evidence of DJD, so in these dogs hip laxity did not result in the development of hip dyspasia. The differences among these breeds are striking, with the highest DI found in the Dachshund, Pekingese, and Miniature Poodle. Note as well that these measurements varied little among individuals, as evidenced by the small standard deviation (SD) relative to the magnitude of the distraction index.

Why do some breeds have looser hips than others? We don't know. Interestingly, the breed with the tightest hips based on DI is the GSD, yet as we've seen this breed has the earliest and most significant development of degenerative joint disease. This seems to fly in the face of the notion among some breeders that loose hips in herding breeds provide greater flexibility that is useful in these working dogs. Even with relatively tight hips, the GSD is most significantly afflicted with joint degeneration that would compromise its function as a working dog. 

Most importantly, these data show that hip laxity alone is not a very good indication of whether a dog will go on to develop joint disease. Dogs could be removed from breeding based on DI that never develop DJD, and others could be allowed to breed based on a score that presents low risk in one breed but high risk in another. 

What about genetic tests for hip dysplasia? There are several published studies that claim to have identified genetic markers associated with the development of hip dysplasia, and some of these have been developed into commercially available tests. However, they are breed specific, and at least one has just been shown to be of very poor predictive value (Manz et al 2017).

Unfortunately, the situation for breeders wishing to reduce the incidence of hip dysplasia remains problematic. The best options remain consideration of the phenotype of related dogs (as in Estimated Breeding Values), and a genomic rather than marker-specific approach to identify genetic risk using thousands of markers (Guo et al 2011).

The genetic architecture of complex diseases like CHD differs fundamentally from that of monogenic disorders. Whereas the latter, by definition, are due to a few genetic changes with high penetrance, the former result from the interplay of a large and unknown number of environmental and genetic factors, most of which have small effects...Instead of basing CHD prediction upon a small number of pre-selected markers, Guo et al. ...proposed the inclusion of all available genomic information in a prognostic model, an approach that recalls strategies in livestock and crop breeding programs for quantitative traits alluded to above. In their `agnostic' approach, all SNPs on a given chip that turn out disease associated in a `learning population' are eventually included in the CHD risk calculated from the genetic profiles of other animals. (Manz et al 2017).

 REFERENCES

​Arnbjerg J. 2017. Hip joint laxity in small dog breeds: a radiological study. SOJ Vet Sci 3(1): 1-5.

Guo G, Z Zhou, Y Wang, K Zhao, L Zhu, G Lust, and others. 2011. Canine hip dysplasia is predictable by genotyping. Osteoarthritis Cartilage 19(4): 420-429. . 

Manz E, B Tellhelm, & M Krawczk. 2017. Prospective evaluation of a patented DNA test for canine hip dysplasia (CHD). PLOS ONE 12(8): e0182093. https://doi.org/10.1371/journal.pone.0182093

Smith, GK, PD Mayhew, AS Kapatkin, PJ McKelvie, FS Shofer, & TP Gregor. 2001. Evaluation of risk factors for degenerative joint disease associated with hip dysplasia in German Shepherd Dogs, Golden Retrievers, Labrador Retrievers, and Rottweilers. JAVMA 219 (12): 1719-1724. 

No dog born with dysplasia. The formation of joints takes place during the first 8 months of life. By 6-8 months of age you can see the the ball positioned into the socket. Prior to this the pelvis is in 4 pieces, and you can watch the formation of joints over the course of the first few months develop. Quality of food, careful weight gain (it is crucial to not  bulk up a puppy), careful handling, do not allow jumping on or off furniture or other objects, running up or down stairs, not over exercising, or causing injury to the hips.