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Motherhood and HRT boost likelihood of knee replacement

Serial motherhood, hormone replacement therapy and early puberty all increase the likelihood of joint surgery, according to a large study to be published in the Annals of the Rheumatic Diseases.

The "Million Women Study" tracked 1.3 million women aged 50 plus for a six-year period to see whether they were admitted to hospital for a knee or hip replacement because of osteoarthritis.

During this period more than 12,000 needed a hip replacement and just under 10,000 needed a knee replacement. Early menstruation boosted the probability of both types of surgery by between 9% and 15%. Every successive birth increased the risk of a hip replacement by 2% and a knee replacement by 8%.

Although use of oral contraceptives did not affect the risk of joint surgery, current use of HRT boosted the chances of a hip replacement by 38% and of a knee replacement by 58% compared with those who had never used HRT.

The authors caution that better use of health services by women on HRT may explain the HRT link.

Osteoarthritis, particularly of the knee, is more common in women than in men. These findings suggest that female sex hormones, particularly oestrogen, may go some way to explain this difference.

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