Hip dysplasia: a significant cause of pain and disability in dogs.
This remains true even after decades of research into its causes and diligent efforts by breeders to reduce risk through selective breeding.
A new review article aimed at veterinarians (Witte 2019) provides a useful summary showing our current understanding of its causes.
According to this review, because the first signs of abnormality appear in young puppies, hip dysplasia is a so-called “developmental disease”.
A key sign of early RISK is “coxofemoral laxity”. This is a loose fit of the head of the femur (ball) in the hip socket.
This looseness means the head of the femur is not held snugly in the socket but can move around. This movement puts abnormal pressures on the sides and rim of the socket. The bone of the socket is thinner at the rim and damage is caused more easily. This poor fit results in deformation of the socket. This continued damage leads to osteoarthritis and the condition of hip dysplasia.
This is a complex condition and specific genes to predict hip dysplasia across breeds have not been found. Simple joint laxity, like “double-jointedness” in humans, carries some form of genetic component. So while genetics plays a role in its development, the condition is complex and clearly polygenic i.e likened to one’s genetics determining if you are going to be tall or not. These “tall” genes are not the same for all humans.
Heritability of hip dysplasia varies widely its values are usually about 0.2-0.3 using the OFA (Orthopedic Foundation for Animals) hip scoring method.
Many non-genetic (environmental) factors are known to affect the risk of developing hip dysplasia.
Some of these factors are very important when raising a puppy.
- Housing on a slippery floor, access to stairs, and some types of exercise can greatly impact the increased risk in puppies.
- Higher weight at birth and while growing (overweight puppies) increases the risk.
- But, dogs raised on farms (firmer footing outdoors) and those born in spring and summer (less likely to be indoors) are less likely to develop hip dysplasia.
- Beside malnutrition or obesity, there is no evidence of the type of diet playing a role in the development of dysplasia.
Once the dog has reached maturity, (18 -24 months) there is little evidence that the amount of exercise alters the progression of osteoarthritis development. Most of the damage occurs before adulthood.
Exercise in an adult dog will only indicate the clinical signs of damage that is already there, i.e. pain and lameness.
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.
For breeders, the responsibility lies not only in considering both dogs’ genetics in mate selection, they also need to consider environmental factors, especially when the puppies are young.
Breeders need to help educate owners about environmental factors that may place risk on their puppies in developing hip dysplasia, especially weight, stairs, and unsuitable exercise and activities.
~ excerpt from Dr Carol Beuchat PhD, Institute of Canine Biology
Witte PG, 2019. Hip dysplasia – understanding the disease. Companion Animal 24:77-81.