Chao Zeng, Jie Wei, Hui Li, Tuo Yang, Fang-Jie Zhang, Ding Pan, Yong-Bing Xiao, Tu-Bao Yang, Guang-Hua Lei

To establish whether there is a relationship between serum magnesium (Mg) concentration and radiographic knee osteoarthritis (OA). There were 2855 subjects in this cross-sectional study. Serum Mg concentration was measured using the chemiluminescence method. Radiographic OA of the knee was defined as changes consistent with Kellgren-Lawrence (K-L) grade 2 on at least 1 side. Mg concentration was classified into 1 of 4 quartiles: ≤ 0.87, 0.88-0.91, 0.92-0.96, or ≥ 0.97 mmol/l. Multivariable logistic analysis was used to test the association between serum Mg and radiographic knee OA after adjustment for potentially confounding factors. The OR with 95% CI for the association between radiographic knee OA and serum Mg concentration were calculated for each quartile. The quartile with the lowest value was regarded as the reference category. Significant association between serum Mg concentration and radiographic knee OA was observed in the model after adjustment for age, sex, and body mass index, as well as in the multivariable model. The multivariable-adjusted OR (95% CI) for radiographic knee OA in the second, third, and fourth serum Mg concentration quartiles were 0.90 (95% CI 0.71-1.13), 0.92 (95% CI 0.73-1.16), and 0.72 (95% CI 0.57-0.92), respectively, compared with the lowest (first) quartile. A clear trend (p for trend was 0.01) was observed. The relative odds of radiographic knee OA was decreased by 0.72 times in the fourth serum Mg quartile compared with the lowest quartile. Serum Mg concentration may have an inverse relationship with radiographic OA of the knee.