Obesity is a primary risk factor for osteoarthritis (OA), and previous studies have shown that dietary content may play an important role in the pathogenesis of cartilage and bone in knee OA. Several previous studies have shown that the ratio of ω‐3 polyunsaturated fatty acids (PUFAs), ω‐6 PUFAs, and saturated fatty acids can significantly influence bone structure and OA progression. However, the influence of obesity or dietary fatty acid content on shoulder OA is not well understood. The goal of this study was to investigate the role of dietary fatty acid content on bone and cartilage structure in the mouse shoulder in a model of diet‐induced obesity. For 24 weeks, mice were fed control or high‐fat diets supplemented with ω‐3 PUFAs, ω‐6 PUFAs, or saturated fatty acids. The humeral heads were analyzed for bone morphometry and mineral density by microCT. Cartilage structure and joint synovitis were determined by histological grading, and microscale mechanical properties of the cartilage extracellular and pericellular matrices were quantified using atomic force microscopy. Diet‐induced obesity significantly altered bone morphology and mineral density in a manner that was dependent on dietary free fatty acid content. In general, high‐fat diet groups showed decreased bone quality, with the ω‐3 diet being partially protective. Cartilage mechanical properties and OA scores showed no changes with obesity or diet. These findings are consistent with clinical literature showing little if any relationship between obesity and shoulder OA (unlike knee OA), but suggest that diet‐induced obesity may influence other joint tissues. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res

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