Knee osteoarthritis is associated with increased prevalence of vertebral fractures despite high systemic bone mineral density: a cross-sectional study in an Asian population

Objectives This study aimed to evaluate the relationship between radiographic knee osteoarthritis and vertebral fractures (VFs) in an Asian population. Methods This cross-sectional study involved data from 1,829 participants of the Fifth Korean National Health and Nutrition Examination Survey. Radiographic knee osteoarthritis was defined as Kellgren-Lawrence (KL) grades >= 2. Prevalent VF was defined as a loss of >= 4 cm of height from the peak height. BMD was measured using dual-energy X-ray absorptiometry, in the lumbar spine and femoral neck. Results In both sexes, the prevalence of VFs increased with age, and was higher in the knee osteoarthritis group than in the control group (in men 13.2 % in osteoarthritis group and 7.9 % in control group; in women 27.7 % in osteoarthritis group and 14.7 % in control group). Age-adjusted BMD at the lumbar spine and femoral neck was significantly higher in the knee osteoarthritis group. In multivariable analysis, KL grade 4 was significantly associated with vertebral fractures in men. In women, there was a significant trend for a positive association between KL grades and vertebral fractures. Conclusions Despite high systemic BMD, knee osteoarthritis was positively associated with VFs. These results suggest that bone quality, and consequently bone strength, may be decreased at the systemic level in knee osteoarthritis.