This article reports the effects of age and lifetime food restriction on development and progression of shoulder joint osteoarthritis in Labrador retrievers. Twenty-four pairs of genetically similar dogs were divided into 2 groups: control-fed (CF) and diet-restricted (DR). The DR group was fed 75% of the amount fed to the CF group. Radiographs taken at 6 and 8 years as well as at "end of life" were compared between groups. Gross pathologic changes were evaluated and histologic changes were categorized based upon regional severity, distribution, and character. Ninety-one percent of dogs were affected by osteoarthritis by their "end-of-life" evaluation. No statistical difference was found between total histopathologic score and principal radiographic findings for CF and DR groups. In addition, the longest-lived dog (a member of the DR group) did not have radiographic evidence of osteoarthritis in either shoulder at any evaluation time, but gross and histopathologic evaluation revealed severe changes consistent with osteoarthritis. The authors concluded that there was a high overall prevalence of osteoarthritis in both groups, and a disparity exists between radiographic evidence of osteoarthritis and gross/histopathologic findings. The DR group had an average life span of 2 years longer than the CF group. Previous work has shown that diet restriction impacts the radiographic prevalence of osteoarthritis in hip joints, but that was not shown in this study.

COMMENTARY: This study provides evidence that it can be very difficult to correlate radiographs of the canine shoulder joint and histopathologic disease. This is a very important finding because, according to the study, the average geriatric Labrador who may limp on a forelimb may or may not have evidence of osteoarthritic disease. If it does, it may or may not be clinically relevant. All of us understand the overall health benefits of keeping our pets healthy and lean, and this study showed that leaner dogs do live longer. Do they live longer with a better quality of life? Intuitively, the answer to this question is easy: of course. However, the study did not overwhelmingly prove a decreased incidence of arthritis in the shoulder joint in Labs that were diet-restricted. Therefore, is it reasonable to assume that if a Lab lives longer but still has arthritis, it is suffering for a longer time?

The effects of lifetime food restriction on the development of osteoarthritis in the canine shoulder. Runge JJ, Biery DN, Lawler DF, et al. VET SURG 37:102-107, 2008.