Tibial cartilage volume change in healthy postmenopausal women: a longitudinal study

Objective: To determine whether the amount of joint cartilage in healthy postmenopausal women is stable or changes over time, and whether oestrogen replacement therapy (ERT) influences this. Design: A cohort study in healthy postmenopausal women without knee pain, initially selected on the basis of having either used ERT long term (more than five years) or never having used ERT. Methods: 81 women (42 taking ERT and 39 non-users) had baseline knee radiographs and magnetic resonance imaging (MRI) on the dominant knee; 57 of these (70%) were followed with repeat MRI approximately 2.5 years later. Knee cartilage volume was measured at baseline and at follow up. Risk factors assessed at baseline, including ERT use, were tested for their association with change in knee cartilage volume over time. Results: 29 subjects who were initially taking ERT and 28 non-users at baseline completed the study. Total tibial articular cartilage decreased, on average, by (mean (SD)) 2.4 (3.2)% per year (95% confidence interval for mean, 1.5% to 3.2%). Average annual reduction in medial and lateral tibial cartilage was 2.4 (3.6)% (1.4% to 3.3%) and 2.3 (4.2)% (1.2% to 3.4%), respectively. No association between ERT and the rate of reduction in cartilage volume was shown. Conclusions: Mean tibial cartilage volume loss in healthy postmenopausal women is between 1.5% and 3.2% a year. Whether this rate of change is similar throughout adult life or in men will require further investigation.