Results of this study showed that by keeping dogs lean, the onset of osteoarthritis was delayed and its severity and prevalence was reduced significantly. Additionally, osteoarthritis prevalence in other joints of lean dogs was decreased and lean dogs had significantly increased longevity.
The principal risk factor, if not the cause, for the development of hip osteoarthritis has been shown to be joint laxity. Previous research has shown the hip-extended radiographic view to underestimate hip laxity, leading to a high rate of false-negative diagnoses at two years of age. Results of this investigation confirmed these findings: hip phenotypes (OFA and osteoarthritis score) were much worse at the end of life than at two years of age. In fact, 55% of dogs scored "normal" at two years of age became dysplastic by the end of life (55% false-negative rate). Regarding osteoarthritis, 83% of dogs that were permitted to get overweight expressed osteoarthritis by the end-of-life, compared to 50% of dogs kept lean.
Key Points from the Nestle Purina Studies:
Keeping dogs lean will reduce the onset, prevalence, and severity of osteoarthritis.
Hip disease (OFA and osteoarthritis score) increased linearly with age. Two years of age is not a biological threshold beyond which hip scores remain constant; a belief espoused by OFA.
Of the dogs scored OFA "normal" at two years of age, 55% went on to become dysplastic. This finding indicates a high rate of false negative diagnosis associated with OFA scoring.
Dogs with radiographic changes have a 3.7-fold increase in the likelihood of developing osteoarthritis.
Unlike OFA score, the PennHIP distraction Index was not confounded by environmental factors such as diet. All dogs were shown to be susceptible to osteoarthritis. The looser-hipped dogs expressed osteoarthritis earlier and with greater severity.
For all dogs but especially for breeding dogs, we recommend regular radiographic hip evaluations over the life of the dog to confirm accuracy of phenotype.