Many studies have looked at the effect of hormones on the knee in women. Changes in knee ligaments have been found during the menstrual cycle and during pregnancy. This is the first report on knee laxity as measured throughout the monthly menstrual cycle.
Twenty-five nonathletic women between the ages of 18 and 30 took part in this study. Knee joint laxity and hormone levels were measured daily for one complete menstrual cycle. Joint laxity refers to how loose a joint is, or how much one side of the knee joint slides against the other. Estrogen, progesterone, and testosterone were included in the hormone measures.
The authors of this study expected to find changes in knee laxity after a rise in hormone levels. They thought estrogen and progesterone together would make a bigger difference than either one alone.
What they actually found was that each hormone affected knee joint laxity. This occurs across the monthly cycle. There was a time delay of three to four days. The effect was greatest when the hormones were combined.
The authors report a wide range of results among women. It’s difficult to know for sure when knee laxity will increase or decrease across the menstrual cycle. This variation makes it difficult to predict and prevent knee injuries. The authors suggest a three-month study as the next step.