Height reduction, determined using knee height measurement as a risk factor or predictive sign for osteoporosis in elderly women

OBJECTIVE: We assessed the value of height reduction, calculated using knee height measurement, as a risk factor or predictive sign for osteoporosis in healthy elderly women. METHODS: In 181 healthy women 76 +/- 5 y of age, height, weight, and knee height were evaluated. Femoral and spine bone mineral densities and body compositions were measured using dual-energy X-ray absorptiometry. In 76 young women 27 +/- 4 y of age, a regression equation to predict height, based on knee height, was derived. Using this equation, maximum attained height and height loss were calculated in elderly women, which was correlated to bone mineral density. RESULTS: The equation to predict height was height (cm) = knee height (cm) x 2.22 + 50.54. The calculated height loss in elderly women was -6.1 +/- 3.8 cm or -0.08 +/- 0.05 cm/y of age. Height loss and hip circumference were significant predictors of spine bone mineral density. In the case of femoral bone mineral density, to the same predictors, a negative effect of waist circumference was added. Women in the highest quintile of height reduction (>0.199 cm/y) had an odds ratio of 4.5 (95% confidence interval 1.56-13.3, P < 0.02) for femoral osteoporosis. CONCLUSION: Knee height can be used as an accurate measurement of height loss in the elderly, which is a significant predictor of femur and spine bone mineral densities, in addition to hip circumference.