The Norwegian Kennel Club has developed a screening program for hip dysplasia in certain breeds, including a standardized radiographic evaluation of hip joints of dogs at 12 or 18 months of age. For this study, puppies were used to investigate environmental factors that may affect development of hip dysplasia in growing dogs. Information from 501 dogs from 103 litters was included. Labrador retrievers and Irish wolfhounds underwent radiographic evaluation at 12 months of age; Newfoundlands and Leonbergers were evaluated at 18 months of age. Questionnaires were completed by breeders, who provided date of birth, litter size, type of housing, and type of bedding in the whelping box; and by dog owners, who noted housing type, presence of children and other animals, types of surfaces exposed to dogs, and details of daily exercise. The study found that puppies that walked on stairs from birth to 3 months of age had an increased risk for developing hip dysplasia. Puppies with off-leash exercise from birth to 3 months of age, born during spring and summer (ie, April-August), and born on a farm had decreased risk. There was significant clustering of dogs with hip dysplasia within litters.

The dogs in this study represented 23% of all registered puppies of these breeds born in Norway in a 3-year period. Overall, 25% had radiographic evidence of hip dysplasia, with the highest percentage in Newfoundlands (36%) and the lowest in wolfhounds (10%). The large number of dogs provided reasonable suggestions for breeders. Exercise on soft ground seemed to have a protective effect, especially if puppies had the summer to enjoy it. This study raised the possibility of manipulating early puppyhood development to reduce phenotypic expression of a dysplastic genotype.—Jonathan Miller, DVM, MS, DACVS

Housing- and exercise-related risk factors associated with the development of hip dysplasia as determined by radiographic evaluation in a prospective cohort of Newfoundlands, Labrador retrievers, Leonbergers, and Irish wolfhounds in Norway. Krontveit RI, Nødtvedt AN, Sævik BK, et al. AM J VET RES 73:838-846, 2012.