Long-term estrogen replacement therapy (ERT) may help protect against knee osteoarthritis (OA), according to preliminay findings by Australian researchers (Ann Rehum Dis. 2001;60:332-336).

The fact that OA is more common in women than men suggests that sex hormone differences play a role in the disease, prompting speculation that ERT in postmenopausal women may help protect joints.

Studies examining the issue have been inconclusive, but radiography -the tool used to measure the presence and degree of OA- is insensitive to changes in joints over a short term. In the new study, however, researchers used magnetic resonance imaging to measure knee cartilage volume in 81 postmenopausal women- 42 current ERT users who had used ERT for at least 5 years and 39 age-matched controls who had never used ERT.

They found (after adjusting for years since menopause, body mass index, age at menopause, age at menopause, and smoking) that women taking ERT had significantly more knee cartilage -about 8%- than did controls. Although the findings suggest that ERT may have a protective effect, the researchers cautioned that such a link "will need to be confirmed in longitudinal studies directly relating these variables."