Objective: To study the association between baseline femoral neck and lumbar spine bone mineral density (BMD), prevalent fractures and incident and progressive radiographic osteoarthritis (ROA) of the knee in men and women.
Methods: A sample of 1403 subjects (829 women and 574 men) was drawn from the Rotterdam Study, a prospective population-based cohort study of the elderly. Incidence and progression of ROA in quartiles of femoral neck (FN) and lumbar spine (LS) BMD were determined using the Kellgren score, and separate analyses were made for men and women. Furthermore, incidence and progression of ROA were compared in subjects with and without a prevalent vertebral or non-vertebral fracture at baseline.
Results: The incidence of knee ROA of subject in the highest FN BMD (10.5%) and LS BMD (14.3%) was significantly higher than of those in the lowest quartiles (3.4% and 3.3% respectively), with corresponding adjusted odds ratios (95% confidence interval) of 2.8 (1.2-6.8) and 4.7 (2.1-10.7). The same trend was seen in the association between LS BMD and the progression of knee ROA, but no association was found between FN BMD and progression of ROA. Separate analyses for men and women both showed significant increased risks in the presence of high baseline BMD, with higher odds ratios in men than in women but larger confidence limits due to lower number of cases in men. Combined incidence and progression of knee ROA in subjects with a prevalent vertebral but not with a prevalent non-vertebral fracture at baseline was 8 times lower than subject without a fracture, independent of baseline BMD.
Conclusions: High systemic BMD at baseline is associated with increased incidence and progression of knee ROA in both men and women, while a prevalent vertebral fracture has a protective effect.