Association between low bone mineral density and subchondral insufficiency fractures of the knee in women, and influence of radial meniscal root tears.

PURPOSE: The purpose of this study was to evaluate the association between systemic low bone mineral density (BMD) and subchondral insufficiency fracture (SIF) of the knee in women, and to explore whether this association is modified by radial meniscal tears. MATERIALS AND METHODS: In this case-control study, women with and without MRI-confirmed SIF who had available dual-energy X-ray absorptiometry T-score measurements were included. Systemic BMD was categorized using T-scores. Multivariable logistic regression models with BMD as the exposure and SIF as the outcome, adjusting for age and body mass index were fitted. An exploratory stratified analysis to assess potential effect modification by meniscal radial tear status was also conducted. RESULTS: A total of 121 women with SIF (mean age, 69.1 ± 7.5 [standard deviation] years) and 124 controls (70.4 ± 8.3 [standard deviation] years) were analyzed. After adjustment, osteoporosis was associated with higher odds of SIF (odds ratio [OR], 2.29; 95% confidence interval [CI]: 1.03-5.09), whereas osteopenia (OR, 1.33; 95% CI: 0.69-2.55) showed no significant association. In exploratory stratified analysis to test for effect modification, there were no significant interactions between low BMD and radial root tears (P-interaction = 0.178). However, small strata likely limited the power to detect a significant effect modification, as evidenced by overlapping wide 95% CIs. CONCLUSION: Osteoporosis is associated with higher odds of SIF of the knee in women, while osteopenia is not.