An update on hip dysplasia in dogs

By Carol Beuchat PhD

Hip dysplasia remains one of the most significant causes of pain and disability in dogs despite decades of research into the causes and diligent efforts by breeders to reduce risk through selective breeding. A new review article aimed at veterinarians provides a useful summary of the current state of our understanding of its causes (Witte 2019). The comments here are detailed in that review.

Hip dysplasia is a so-called "developmental disease", because the first signs of abnormality appear in young puppies.

​A key sign of early risk is "coxofemoral laxity", a loose fit of the head of the femur in the hip socket. This looseness means the head of the femur is not held snugly in the socket but can move around, putting abnormal pressures on the sides and rim of the socket. This poor fit results in deformation of the socket and ultimately leads to osteoarthritis and the condition of hip dysplasia.
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Genetics clearly plays a role in the development of hip dysplasia. However, the condition is complex and clearly polygenic and specific genes that are predictive of hip dysplasia across breeds have not been found.

Top: Femoral head well-seated in the hip socket with good coverage by the acetabular rim. The loading forces will be evenly distributed over a large surface area. Bottom: Femoral head is subluxated (pulled away) from the hip socket as in a hip with laxity. The loading forces will not be evenly distributed but focused on the weaker rim of the socket. (Witte 2019)

Heritability is the fraction of the variation in hip phenotype that is accounted for by variation in genotype. The higher the heritability of a trait, the more it will respond to selection. Heritability of hip dysplasia varies widely depending on the breed, the sample population, and the criterion used to assess phenotype. Values for heritability are usually about 0.2-0.3 using the OFA (Orthopedic Foundation for Animals) hip scoring method, while much higher heritability (0.8) has been reported in some dogs evaluated using PennHIP (Pennsylvania Hip Improvement Program). 
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A number of non-genetic (environmental) factors are known to affect the risk of developing hip dysplasia, and some of these appear to be especially critical to manage properly in the puppy. Housing on a slippery floor, access to stairs, and some types of exercise can significantly increase risk in puppies. Higher weight at birth and while growing elevates risk. On the other hand, dogs raised on farms and those born in spring and summer are less likely to develop hip dysplasia. Aside from nutritional deficiencies, or overconsumption that leads to overweight, there is no evidence that the type of the diet plays a role in development of dysplasia. Although exercise in the adult might lead to clinical signs of pain or lameness, there is little evidence that the amount of exercise alters the progression of development of osteoarthritis once the dog matures. Dogs neutered before 6 months have a higher risk of developing hip dysplasia.

Managing the risk of hip dysplasia remains a challenge for breeders and dog owners. Breeders must consider both genetics in mate selection and environmental factors, especially when the puppies are young. When puppies go to their new homes, owners must be educated about the factors that elevate the risk of developing hip dysplasia, especially weight, stairs, and unsuitable exercise and activities.
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(Witte 2019)

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You can learn more about hip and elbow dysplasia in ICB's online course "Understanding Hip & Elbow Dysplasia", which covers the most up-to-date information about causes, treatment, and prevention.

Learn more HERE.​​​​

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REFERENCES
Witte PG, 2019. Hip dysplasia - understanding the disease. Companion Animal 24:77-81.

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